How will a limit order be executed when the stock market opens if there is a large change from the price of the day before?
The next day the market opens trading at 10.50, You haven't specified whether you limit order for $10.10 is to buy or sell. When the trading opens next day, it follows the same process of matching the orders. So if you have put a limit order to buy at $10.10 and there is no sell order at that price, your trade will not go through. If you have placed a limit sell order at $10.10 and there is a buyer at or higher price, it would go through. The Open price is the price of the first trade of the day.
As others have stated, the current price is simply the last price at which the security traded. For any given tick, however, there are many bid-ask prices because securities can trade on multiple exchanges and between many agents on a single exchange. This is true for both types of exchanges that Chris mentioned in his answer. Chris' answer is pretty thorough in explaining how the two types of exchanges work, so I'll just add some minor details. In exchanges like NASDAQ, there are multiple market makers for most relatively liquid securities, which theoretically introduces competition between them and therefore lowers the bid-ask spreads that traders face. Although this results in the market makers earning less compensation for their risk, they hope to make up the difference by making the market for highly liquid securities. This could also result in your order filling, in pieces, at several different prices if your brokerage firm fills it through multiple market makers. Of course, if you place your order on an exchange where an electronic system fills it (the other type of exchange that Chris mentioned), this could happen anyway.  In short, if you place a market order for 1000 shares, it could be filled at several different prices, depending on volume, multiple bid-ask prices, etc. If you place a sizable order, your broker may fill it in pieces regardless to prevent you from moving the market. This is rarely a problem for small-time investors trading securities with high volumes, but for investors with higher capital like institutional investors, mutual funds, etc. who place large orders relative to the average volume, this could conceivably be a burden, both in the price difference across time as the order is placed and the increased bookkeeping it demands.  This is tangentially related, so I'll add it anyway. In cases like the one described above, all-or-none (AON) orders are one solution; these are orders that instruct the broker to only execute the order if it can be filled in a single transaction. Most brokers offer these, but there are some caveats that apply to them specifically. (I haven't been able to find some of this information, so some of this is from memory).  All-or-none orders are only an option if the order is for more than a certain numbers of shares. I think the minimum size is 300 or 400 shares.  Your order won't be placed until your broker places all other orders ahead of it that don't have special conditions attached to them.  I believe all-or-none orders are day orders, which means that if there wasn't enough supply to fill the order during the day, the order is cancelled at market close.  AON orders only apply to limit orders. If you want to replicate the behavior of a market order with AON characteristics, you can try setting a limit buy/sell order a few cents above/below the current market price. "&gt; Is your time frame any longer than intraday? I imagine you wouldn't want to carry that risk overnight if you're a broker or selling a route..  Most brokers these days are executing in an agent capacity, so they're never holding the risk. They execute what they can, the customer keeps what they can't.   &gt; So, say for instance you join a bid a few levels down, you aren't really get filled, you start hitting the offer and eventually you realize you're competing with someone for the shares offered, so you take out the price level and bid on all the exchanges so that you're first on the bid at that level, then repeat until someone that can match your appetite starts to fill you on the bid?  Lifting* the offer (hit bids, lift offers). And I suppose that's a stategy, albeit a somewhat simple one. Passive routing strategies differ from firm to firm and algo to algo. What is your customer going to think if you bid up a new price level only for the stock to rally completely away from it?  &gt; Right, so say you need 100k shares, there are 10k offered at 9.98, 25k offered at 9.99, and 65k at 10.00, you might just enter an intermarket sweep order of 100k @ 10 limit and hope that you can get most of the shares off before everyone can cancel? I imagine there has to be a lot of bidding it up to attract sellers and then letting people take out your bids all day...  ""Bidding it up to attract sellers"" sounds an awful lot like [spoofing](https://en.wikipedia.org/wiki/Spoofing_(finance\)), just a heads up. Sure though, if you want to tighten a spread or create new levels with aggressive passive liquidity, that is a strategy. The same caveats as I mentioned above apply.  Anyway, if market impact isn't an issue for the customer, sure, take liquidity until you're filled. Don't forget about getting good size done in the opening and closing auctions (MOO/MOC). If you're too passive you risk the market moving away from you and pissing off the customer. If you're too aggressive you risk moving the market too much and pissing off the customer." I can't say I know everything about the underlying details, but from what I understand, your limit buy adds to the bid side of open orders, and one possibility is that someone placed a market order to sell when the bid price for the stock fell to $10 which was matched to your open limit order. So using your terminology, I would say the spot bid price is what fell to $10, even if for a brief moment. Whether or not it is possible for your order to be filled when the limit buy price is deeper than the current bid price is beyond me. It may have something to do with lot sizes. "During the day, market and limit orders are submitted at any time by market participants and there is a bid and an ask that move around over time.  Trades occur whenever a market order is submitted or a limit order is submitted that at a price that matches or exceeds an existing limit order.  If you submit a market order, it may consume all best-price limit orders and you can get multiple prices, changing the bid or ask at the same time.  All that stuff happens during the trading day only. What happens at the end of the day is different.  A bunch of orders that were submitted during the day but marked as ""on close"" are aggregated with any outstanding limit orders to create a single closing price according to the algorithm established by the exchange.  Each exchange may handle the details of this closing event differently.  For example, the Nasdaq's closing cross or the NYSE's closing auction. The close is the most liquid time of the day, so investors who are trading large amounts and not interested in intraday swings will often submit a market-on-close or limit-on-close order.  This minimizes their chance of affecting the price or crossing a big spread.  It's actually most relevant for smaller stocks, which may have too little volume during the day to make big trades, but have plenty at the close.  In short, the volume you see is due to these on-close orders. The spike in volume most likely has no special information about what will happen overnight or the next day.  It's probably just a normal part of the market for illiquid stocks." Obvious answer but the limit order should be set at the price that you are willing to pay :). More usefully, if you want a decent chance of the order filling in short notice you should place the order one price tick above the current highest buyer (bid price). As long as high frequency trading remains alive I would advise against ever using market orders, these algorithmic trades can occasionally severely distort the price of a security in a fraction of a second. So if your market order happens to fill in during such a distortion you might end up massively overpaying/underselling. Stop orders and stop limit orders typically do not execute during extended hours after the general market session has closed. Stop orders are market orders and market orders especially are not executed during extended hours. Although there are exceptions because a broker can say one thing and do another thing with the way order types are presented to customers vs what their programming actually does. The regulatory burden is a slap on the wrist, so you need to ask the broker what their practices are. Orders created during normal market hours do not execute in extended sessions, different orders would have to be made during the extended session. Your stop order should execute if the normal market hour price stays below your stop price. So a stop limit would actually be worse here, because a stop limit will create a limit order which may never get hit (since it is above the best bid best ask) "Correcting Keith's answer (you should have read about these details in the terms and conditions of your bank/broker): Entrustment orders are like a ""soft"" limit order and meaningless without a validity (which is typically between 1 and 5 days). If you buy silver at an entrustment price above market price, say x when the market offer is m, then parts of your order will likely be filled at the market price.  For the remaining quantity there is now a limit, the bank/broker might fill your order over the next 5 days (or however long the validity is) at various prices, such that the overall average price does not exceed x. This is different to a limit order, as it allows the bank/broker to (partially) buy silver at higher prices than x as long as the overall averages is x or less.  In a limit set-up you might be (partially) filled at market prices first, but if the market moves above x the bank/broker will not fill any remaining quantities of your order, so you might end up (after a day or 5 days) with a partially filled order. Also note that an entrustment price below the market price and with a short enough validity behaves like a limit price. The 4th order type is sort of an opposite-side limit price: A stop-buy means buy when the market offer quote goes above a certain price, a stop-sell means sell when the market bid quote goes below a certain price. Paired with the entrusment principle, this might mean that you buy/sell on average above/below the price you give. I don't know how big your orders are or will be but always keep in mind that not all of your order might be filled immediately, a so-called partial fill.  This is particularly noteworthy when you're in a pro-rata market." "The ""price"" is the price of the last transaction that actually took place. According to Motley Fool wiki: A stock price is determined by what was last paid for it. During market hours (usually weekdays from 9:30AM-4:00PM eastern), a heavily traded issue will see its price change several times per second. A stock's price is, for many purposes, considered unchanged outside of market hours. Roughly speaking, a transaction is executed when an offer to buy matches an offer to sell. These offers are listed in the Order Book for a stock (Example: GOOG at Yahoo Finance).  This is actively updated during trading hours. This lists all the currently active buy (""bid"") and sell (""ask"") orders for a stock, and looks like this:  You'll notice that the stock price (again, the last sale price) will (usually*) be between the highest bid and the lowest ask price. * Exception: When all the buy or sell prices have moved down or up, but no trades have executed yet."