Market order vs. limit order.
Limit orders are buy or sell orders for a quantity of a financial asset at a set price or better. You can also choose whether the exchange can partially fill your limit order or if it must be completely filled. In the latter case, if the exchange cannot fully fill your order, it will not execute it at all.
Market orders can only be filled with existing limit orders. Not everyone wants to take the available market price when trading or investing, so a limit order is a good alternative. You can use limit orders to plan your trades in advance, without needing to be at your trading desk.
