A market order is an order to buy or sell a security at the current market price. A market order typically ensures an execution, but it does not guarantee a specified price. It is executed at the price of the stock at the moment the transaction is presented for execution on exchange or at a dealer. Because there may be, for example, a small delay or other orders may arrive at the point of execution prior to your order, the execution price may be different from the one you saw when you clicked 'buy' or 'sell.' For instance, if you submit a market order to buy a popular stock you see quoted at $10 per share, by the time that order is executed, even if only moments later, the price may have dropped to $9.90 per share or risen to $10.10 per share. In a volatile market, the price difference could be even more significant.