What does net selling or buying of a stock mean?
Consider the mechanic which actually drives the 'price' of a stock. In simplest terms, the 'price' of a stock is the price at which the most recent trade occurred. ie: if the price of IBM is $100/share, that means the last time someone bought IBM stock, they paid $100. Above and below the 'spot price', are dozens/hundreds/thousands of buyers and sellers who have placed orders that no one is yet willing to match. ie: if IBM's spot price is at $100, there could still be 10,000 people willing to sell for $101 (called the 'ask' price, for the lowest price someone is currently willing to sell at), and 15,000 willing to buy for $99 (called the 'bid' price, for the highest price someone is currently willing to buy for).  Until someone is willing to buy for $101, then no one will be able to sell at $101. Until someone is willing to sell for $99, no one will be able to buy for $99. Typically orders are placed in the market at a particular limit. Meaning that those orders to buy at $99/sell at $101 are already in the 'system', and will be matched immediately as soon as someone is willing to meet the price on the other side. Now consider general market economics: high demand drives up price, and high supply drives down price. If the details above for IBM were yesterday, and today some news came out that IBM was laying off employees, imagine that another 10,000 people who held shares wanted to sell. Now there would be 20,000 sellers and only 15,000 buyers. If those new sellers were aggressive about wanting to sell, they would have to drop their price to $99, to match the highest buyers in the market. Put together, this means that as more sellers enter the market, supply of shares increases, driving down price. Conversely, as more buyers enter the market, demand for shares increases, driving up share price. As a result of the above, you can say that (all else being equal) if price for a stock goes up, there were more buyers that day, and if price goes down, there were more sellers that day. On the face of it, that is not necessarily true, because you could have the same number of buyers and sellers, one side could have simply decreased/increased their acceptable price to match the other side. What does it mean when some one says that today there was a lot of net selling or buying in a stock. What does it mean because for every selling there is also a buying going on then how can you determine a selling or buying ? Generally if the price of stock has gone down compared to previous day, the trend is of selling. As the price can be volatile, there maybe few trades that are above close price of previous day, or below close price of previous day.  How can you calculate average trade price for a stock It is simple {sum of all [price*quantity]}/quantity. Related question Equity market inflow meaning "I'm not sure the term actually has a clear meaning. We can think of ""what does this mean"" in two ways: its broad semantic/metaphorical meaning, and its mechanical ""what actual variables in the market represent this quantity"". Net buying/selling have a clear meaning in the former sense by analogy to the basic concept of supply and demand in equilibrium markets. It's not as clear what their meaning should be in the latter sense. Roughly, as the top comment notes, you could say that a price decrease is because of net selling at the previous price level, while a price rise is driven by net buying at the previous price level. But in terms of actual market mechanics, the only way prices move is by matching of a buyer and a seller, so every market transaction inherently represents an instantaneous balance across the bid/ask spread. So then we could think about the notion of orders. Actual transactions only occur in balance, but there is a whole book of standing orders at various prices. So maybe we could use some measure of the volume at various price levels in each of the bid/ask books to decide some notion of net buying/selling. But again, actual transactions occur only when matched across the spread. If a significant order volume is added on one side or the other, but at a price far away from the bid/offer - far enough that an actual trade at that price is unlikely to occur - should that be included in the notion of net buying/selling? Presumably there is some price distance from the bid/offer where the orders don't matter for net buying/selling. I'm sure you'd find a lot of buyers for BRK.A at $1, but that's completely irrelevant to the notion of net buying/selling in BRK.A. Maybe the closest thing I can think of in terms of actual market mechanics is the comparative total volumes during the period that would still have been executed if forced to execute at the end of period price. Assuming that traders' valuations are fixed through the period in question, and trading occurs on the basis of fundamentals (which I know isn't a good assumption in practice, but the impact of price history upon future price is too complex for this analysis), we have two cases. If price falls, we can assume all buyers who executed above the last price in the period would have happily bought at the last price (saving money), while all sellers who executed below the last price in the period would also be happy to sell for more. The former will be larger than the latter. If the price rises, the reverse is true."
"The stock market is not a zero-sum game.  Some parts are (forex, some option trading), but plain old stock trading is not zero sum. That is to say, if you were to invest ""at random"", you would on average make money.  That's because the market as a whole makes money - it goes up over time (6-10% annually, averaged over time).  That's because you're not just gambling when you buy a stock; you're actually contributing money to a company (directly or indirectly), which it uses to fund activities that (on average) make money.  When you buy Caterpillar stock, you're indirectly funding Caterpillar building tractors, which they then sell for a profit, and thus your stock appreciates in value.  While not every company makes a profit, and thus not every stock appreciates in true value, the average one does. To some extent, buying index funds is pretty close to ""investing at random"".  It has a far lower risk quotient, of course, since you're not buying a few stocks at random but instead are buying all stocks in an index; but buying stocks from the S&P 500 at random would on average give the same return as VOO (with way more volatility). So for one, you definitely could do worse than 50/50; if you simply sold the market short (sold random stocks short), you would lose money over time on average, above and beyond the transaction cost, since the market will go up over time on average. Secondly, there is the consideration of limited and unlimited gains or losses. Some trades, specifically some option trades, have limited potential gains, and unlimited potential losses. Take for example, a simple call option.  If you sell a naked call option - meaning you sell a call option but don't own the stock - for $100, at a strike price of $20, for 100 shares, you make money as long as the price of that stock is under $21.  You have a potential to make $100, because that's what you sold it for; if the price is under $20, it's not exercised, and you just get that $100, free.   But, on the other hand, if the stock goes up, you could potentially be out any amount of money.  If the stock trades at $24, you're out $400-100 = $300, right?  (Plus transaction costs.)   But what if it trades at $60?  Or $100?  Or $10000?  You're still out 100 * that amount, so in the latter case, $1 million.  It's not likely to trade at that point, but it could. If you were to trade ""at random"", you'd probably run into one of those types of situations.  That's because there are lots of potential trades out there that nobody expects anyone to take - but that doesn't mean that people wouldn't be happy to take your money if you offered it to them.   That's the reason your 16.66 vs 83.33 argument is faulty:  you're absolutely right that if there were a consistently losing line, that the consistently winning line would exist, but that requires someone that is willing to take the losing line.  Trades require two actors, one on each side; if you're willing to be the patsy, there's always someone happy to take advantage of you, but you might not get a patsy." "I think you've got basics, but you may have the order / emphasis a bit wrong. I've changed the order of the things you've learned in to what I think is the most important to understand: Owning a stock is like owning a tiny chunk of the business Owning stock is owning a tiny chunk of the business, it's not just ""like"" it. The ""tiny chunks"" are called shares, because that is literally what they are, a share of the business. Sometimes shares are also called stocks. The words stock and share are mostly interchangeable, but a single stock normally means your holding of many shares in a business, so if you have 100 shares in 1 company, that's a stock in that company, if you then buy 100 shares in another company, you now own 2 stocks. An investor seeks to buy stocks at a low price, and sell when the price is high. Not necessarily. An investor will buy shares in a company that they believe will make them a profit. In general, a company will make a profit and distribute some or all of it to shareholders in the form of dividends. They will also keep back a portion of the profit to invest in growing the company. If the company does grow, it will grow in value and your shares will get more valuable. Price (of a stock) is affected by supply/demand, volume, and possibly company profits The price of a share that you see on a stock ticker is the price that people on the market have exchanged the share for recently, not the price you or I can buy a share for, although usually if people on the market are buying and selling at that price, someone will buy or sell from you at a similar sort of price. In theory, the price will be the companies total value, if you were to own the whole thing (it's market capitalisation) divided by the total number of shares that exist in that company. The problem is that it's very difficult to work out the total value of a company. You can start by counting the different things that it owns (including things like intellectual property and the knowledge and experience of people who work there), subtract all the money it owes in loans etc., and then make an allowance for how much profit you expect the company to make in the future. The problem is that these numbers are all going to be estimates, and different peoples estimates will disagree. Some people don't bother to estimate at all. The market makers will just follow supply and demand. They will hold a few shares in each of many companies that they are interested in. They will advertise a lower price that they are willing to buy at and a higher price that they will sell at all the time. When they hold a lot of a share, they will price it lower so that people buy it from them. When they start to run out, they will price it higher. You will never need to spend more than the market makers price to buy a share, or get less than the market makers price when you come to sell it (unless you want to buy or sell more shares than they are willing to). This is why stock price depends on supply and demand. The other category of people who don't care about the companies they are trading are the high speed traders. They just look at information like the past price, the volume (total amount of shares being exchanged on the market) and many other statistics both from the market and elsewhere and look for patterns. You cannot compete with these people - they do things like physically locate their servers nearer to the stock exchanges buildings to get a few milliseconds time advantage over their competitors to buy shares quicker than them." "Mathematically it's arbitrary - you could just as easily use the bid or the midpoint as the denominator, so long as you're consistent when comparing securities.  So there's not a fundamental reason to use the ask.  The best argument I can come up with is that most analysis is done from the buy side, so looking at liquidity costs (meaning how much does the value drop instantaneously purely because of the bid-ask spread) when you buy a security would be more relevant by using the ask (purchase price) as the basis. Meaning, if a stock has a bid-ask range of $95-$100, if you buy the stock at $100 (the ask), you immediately ""lose"" 5% (5/100) of its value since you can only sell it for $95." "I don't think the advice to take lots more risk when young makes so much sense. The additional returns from loading up on stocks are overblown; and the rocky road from owning 75-100% stocks will almost certainly mess you up and make you lose money. Everyone thinks they're different, but none of us are. One big advantage of stocks over bonds is tax efficiency only if you buy index funds and don't ever sell them. But this does not matter in a retirement account, and outside a retirement account you can use tax-exempt bonds. Stocks have higher returns in theory but to have a reasonable guarantee of higher returns from them, you need around a 30-year horizon. That is a long, long time. Psychologically, a 60/40 stocks/bonds portfolio, or something with similar risk mixing in a few more alternative assets like Swenson's, is SO MUCH better. With 100% stocks you can spend 10 or 15 years saving money and your investment returns may get you nowhere. Think what that does to your motivation to save. (And how much you save is way more important than what you invest in.) The same doesn't happen with a balanced portfolio. With a balanced portfolio you get reasonably steady progress. You can still have a down year, but you're a lot less likely to have a down decade or even a down few years. You save steadily and your balance goes up fairly steadily. The way humans really work, this is so important. For the same kind of reason, I think it's great to buy one fund that has both stocks and bonds in there. This forces you to view the thing as a whole instead of wrongly looking at the individual asset class ""buckets."" And it also means rebalancing will happen automatically, without having to remember to do it, which you won't. Or if you remember you won't do it when you should, because stocks are doing so well, or some other rationalization. Speaking of rebalancing, that's where a lot of the steady, predictable returns come from if you have a nice balanced portfolio. You can make money over time even if both asset classes end up going nowhere, as long as they bounce around somewhat independently, so you'll buy low and sell high when you rebalance. To me the ideal is an all-in-one fund that aims for about 60/40 stocks/bonds level of risk, somewhat more diversified than stocks/bonds is great (international stock, commodities, high yield, REIT, etc.). You can just buy that at age 20 and keep it until you retire. In beautiful ideal-world economic theory, buy 90% stocks when young. Real world with human brain involved: I love balanced funds. The steady gains are such a mental win. The ""target retirement"" funds are not a bad option, but if you buy the matching year for your age, I personally wish they had less in stocks. If you want to read more on the ""equity premium"" (how much more you make from owning stocks) here are a couple of posts on it from a blog I like: Update: I wrote this up more comprehensively on my blog," "fennec has a very good answer but i feel it provides too much information. So i'll just try to explain what that sentence says. Put option is the right to sell a stock. ""16 puts on Cisco at 71 cents"", means John comes to Jim and says, i'll give you 71 cent now, if you allow me to sell one share of Cisco to you at $16 at some point in the future ( on expiration date).  NYT quote says 1000 puts that means 1000 contracts - he bought a right to sell 100,000 shares of Cisco on some day at $16/share. Call option - same idea: right to buy a stock." "Suppose the stock is $41 at expiry. The graph says I will lose money. I think I paid $37.20 for (net debit) at this price. I would make money, not lose. What am I missing? The `net debit' doesn't have anything to do with your P/L graph. Your graph is also showing your profit and loss for NOW and only one expiration. Your trade has two expirations, and I don't know which one that graph is showing. That is the ""mystery"" behind that graph. Regardless, your PUTs are mitigating your loss as you would expect, if you didn't have the put you would simply lose more money at that particular price range. If you don't like that particular range then you will have to consider a different contract. it was originally a simple covered call, I added a put to protect from stock going lower.. Your strike prices are all over the place and NBIX has a contract at every whole number.... there is nothing simple about this trade. You typically won't find an ""always profitable"" combination of options. Also, changes in volatility can distort your projects greatly." "An attempt at a simple answer for the normal investor: A normal investor buys stock then later sells that stock. (This is known as ""going long"", as opposed to ""going short"").  For the normal investor, a stop order (of either kind) is only used when selling. A stop-loss sell order (or stop sell) is used to sell your stock when it has fallen too much in price, and you don't want to suffer more losses.  If the stock is at $50, you could enter a stop sell at $40, which means if the stock ever falls to $40 or lower, your stock will be sold at whatever price is available (e.g. $35). A stop-loss limit sell order (or stop limit sell) is the same, except you are also saying ""but don't sell for less than my limit price"".  So you can enter a stop limit sell at $40 with a limit of $39, meaning that if the stock falls to $40, you will then have a limit order in effect to sell the stock at $39 or higher.  Thus your stock will never be sold at $35 or any value below $39, but of course, if the stock falls fast from $40 to $35, your limit sell at $39 will not be done and you will be left still owning the stock (worth at that moment $35, say)." "If I invest in individual stocks I will, from time to time, sell stocks that aren't performing well. If the value of my portfolio has gone up by 10%, then the value of my portfolio has gone up by 10%, regardless of whether selling those stocks is labeled as ""delete[ing] failures"". Same thing for mutual funds: selling underperforming stocks is perfectly ordinary, and calling it ""delete[ing] failures"" in order to imply some sort of dishonesty is simply dishonest."