How might trading volume affect future share price?
There is no direct relationship between volume and stock price. High volume indicates how much stock is changing hands. That can be because people are enthusiastically buying OR enthusiastically selling... and their reasons for doing so may not agree with your own sense of the future value of the stock. Higher volume may mean that the price is more likely to change during the day, but it can be in either direction -- or in no direction at all if there isn't a general agreement on how to react to some piece of news. It's a possibly interesting datum, but it means nothing in isolation. You can't tell for sure.  If there was such a technique then everyone would use it and the price would instantly change to reflect the future price value. However, trade volume does say something.  If you have a lemonade stand and offer a large glass of ice cold lemonade for 1c on a hot summer day I'm pretty sure you'll have high trading volume.  If you offer it for $5000 the trading volume is going to be around zero. Since the supply of lemonade is presumably limited at some point dropping the price further isn't going to increase the number of transactions.   Trade volumes reflect to some degree the difference of valuations between buyers and sellers and the supply and demand.  It's another piece of information that you can try looking at and interpreting.  If you can be more successful at this than the majority of others on the market (not very likely) you may get a small edge.  I'm willing to bet that high frequency trading algorithms factor volume into their trading decisions among multiple other factors. "There tends to be high volume around big changes in stock price. The volume of a stock does not remain constant and the term ""fat fingers"" can influence price.--> http://www.bloomberg.com/news/2014-10-01/that-japanese-fat-finger-can-absolutely-happen-in-u-s-.html That being said keshlam is 99% right when it comes to a stock moving when their is no news or earnings announcements. Check out these papers. http://onlinelibrary.wiley.com/doi/10.1111/j.1475-6803.2010.01285.x/full They do a time series analysis to try and predict future prices off of past demand during news events. They forecast using auto-regressive models.  google ""forecasting autoregressive model"" and the upenn lecture will be helpful. I would post another link but I cannot because I do not have enough rep/ This is more of a quant question. Hope this helps. JL" As said previously, most of the time volume does not affect stock prices, except with penny stocks. These stocks typically have a small volume in the 3 or 4 figure range and because of this they typically experience very sharp rises and drops in stock prices, contrasting normal stocks that go up and down constantly every minute. Volume is not one thing you should be looking at when analyzing a stock in most cases, since it is simply the number of people of trades made in a day. That has no effect on the value of the company, whereas looking at P/E ratios, dividend growth, etc all can be analyzed to see if a company is growing and is doing well in its field. If I buy an iPhone, it doesn't matter if 100 other people or 100,000 other people have bought it as well, since they won't really affect my experience with the product. Whereas the type of iPhone I buy will. Volumes are used to predict momentum of movement, not the direction of it. Large trading volumes generally tend to create a price breakout in either positive or negative direction. Especially in relatively illiquid stocks (like small caps), sudden volume surges can create sharp price fluctuations.
"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." I would say the most challenging fact for this assertion is that HFT firms operate with extremely limited capital bases. For a stock with say 10m shares ADV, even a very large and successful HFT strategy might use a position limit of no more than 5000 shares.  That is to say if you sum up and net the buys and sells for a stock across the day the HFT firm will never exceed 10,000 shares (2x position limits assuming it completely flipped) on a stock that trades 10,000,000 shares on a given day. The high volumes are attained through high turnover, the strategy might trade up to 500,000 shares (or 5% of the volume) attaining a 50x turnover.  But that brings me back to the original point. In the market microstructure literature market impact generally has been found to scale linearly or even sub-linearly for net volume executed.   If I alternate between thousands of 1 lot buy and sell orders, it would be very difficult for me to move the market because the market impact of every one of my buy orders roughly cancels the market impact of my almost exactly equal number of sell orders.   There might be a higher-order mechanism at work, but I'm genuinely curious what you think it might be. How could strategies that attain such small net positions have such out-sized impact on market direction? Can someone please explain how traders and investors use this price difference to trade? People use the price difference for small arbitrage between the futures and spot markets, where the larger spreads are reflected in the options markets. The spread in the options market dictates the VIX which many investors also use in their decision making process.  And most importantly how the futures market affects subsequent moves in the stock market? The futures market effects the stock market where large contract holders move the entire futures price. This causes reactionary moves amongst all of the aforementioned arbitragers, who are hedged between the futures and spot markets. With the /ES this is reflected down to actual individual stocks based on their weightings in the S&P 500 index. Many of those stocks have smaller companies that are also linked to them, such as a widget manufacturer for a gigantic ACME corporation listed in the S&P 500. "Though it seems unintuitive, you should rationally ignore the past performance of this stock (including the fact that it's at its 52-week high) and focus exclusively on factors that you believe should affect it moving forward.  If you think it's going to go up even further,  more than the return on your other options for where to put the money, keep the stock.  If you think it's peaked and will be going down, now's a good time to sell. To put it another way: if you didn't already have this stock, would you buy it today? Your choice is just about the same: you can choose between a sum of cash equal to the present market value of the shares, OR the shares.   Which do you think is worth more? You also mentioned that you only have 10 stocks in the portfolio.  Some are probably a larger percentage than others, and this distribution may be different than what you want in your portfolio.  It may be time to do some rebalancing, which could involve selling some shares where your position is too large (as a % of your portfolio) and using the proceeds toward one or more categories you're not as invested in as you would like to be.  This might be a good opportunity to increase the diversity in your portfolio. If part of your reward and motivation for trading is emotional, not purely financial, you could sell now, mark it as a ""win,"" and move on to another opportunity.  Trading based on emotions is not likely to optimize your future balance, but not everybody is into trading or money for money's sake.  What's going to help you sleep better at night and help boost your quality of life?  If holding the stock will make you stress and regret a missed opportunity if it goes down, and selling it will make you feel happy and confident even if it still goes up more (e.g. you interpret that as further confirming that you made a good pick in the first place), you might decide that the risk of suboptimal financial returns (from emotion-based trading) is acceptable.  As CQM points out, you could also set a trailing sell order to activate only when the stock is a certain percentage or dollar amount below whatever it peaks at between the time you set the order and the time it fires/expires; the activation price will rise with the stock and hold as it falls." The market maker will always compare the highest bid and the lowest ask. A trade will happen if the highest bid is at least as high as the lowest ask. Adding one share (or a million shares) at a higher asking price, here: $210 instead of $200, will not have any effect at all. Nobody will buy the share.  Adding a bid for one share (or a million shares) at a higher bid price will trigger a sale. If you bid $210 for one share, you will pay $210 for one of the shares that were offered at $200. If you have $210 million in cash and add a bid for 1,000,000 AAPL at $210, you will pay $210 for all shares with an ask of $200.00, then $200.01, then $200.02 until you either bought all shares with an ask up to $210, or until you bought a million shares.  With AAPL, you probably bid the price up to $201 with a million shares, so you made lots of people very happy while losing about 10 million dollars. So let's say this is a much smaller company.  You have driven the share price up to $210, but there is nobody else bidding above $200. So nobody is going to buy your shares. Until some people think there is something going on and enter higher bids, but then some people will take advantage of this and ask lower than your $210. And there will be more people trying to make cash by selling their shares at a good price than people tricked into bidding over $200, so it is most likely that you lose out.  (This completely ignores legality; attempting to do this would be market manipulation and in many countries illegal. I don't know if losing money in the process would protect you from criminal charges). A stock is only worth what someone is willing to pay for it. If it trades different values on different days, that means someone was willing to pay a higher price OR someone was willing to sell at a lower price.  There is no rule to prevent a stock from trading at $10 and then $100 the very next trade... or $1 the very next trade. (Though exchanges or regulators may halt trading, cancel trades, or impose limits on large price movements as they deem necessary, but this is beside the point I'm trying to illustrate). Asking what happens from the close of one day to the open of the next is like asking what happens from one trade to the next trade... someone simply decided to sell or pay a different price.  Nothing needs to have happened in between. Trading volumes are higher at the end of the day as many traders close their open positions. In the morning however, traders incorporate various factors like performance of worldwide markets overnight, any corporate or government announcements, global macro events, etc. "Stock price is set to the price with the highest transaction volume at any given time.  The stock price you cited was only valid in the last transaction on a specific stock exchange. As such it is more of an ""historic"" value. Next trade will be done with the next biggest volume. Depending on the incoming bids and asks this could be higher or lower, but you can assume it will not be too far off if there is no crash underway. Simple example stock exchange:"