A Limit Order is a way of trading at the price specified by the trader. Traders can specify the minimum price they want to buy if they want to go long, and the highest price they want to sell when going short. An order is placed only when it reaches the specified price, which is the price set by the trader, and it may take longer until the order is filled if there are no orders available for the particular price. Due to this, long Limit Orders and short Limit Orders are usually set at a price lower and higher than the last traded price respectively. On the other hand, if the Limit Order price is set above or below respectively, then the order will be filled against the best available market price until it reaches the specified price. The unfilled contracts will remain in the order book as a Limit Order.
When the Limit Order is submitted, it will be placed in the order book until it is matched or canceled. However, the way the order is filled may differ according to the Time in Force* option which is often used in variation with the Market Order. Therefore you can use the Limit Order to partially fill a Market Order and leave the remaining unfilled orders as Limit Orders.