What does fill policy mean?

Fill policy defines the rules under which an order is executed. Typical options include FOK (Fill or Kill), IOC (Immediate or Cancel), and GTC (Good Till Cancelled). FOK requires the entire order to be filled immediately or else it is canceled. IOC allows partial fills, with unfilled portions canceled automatically. GTC keeps the order valid until the trader cancels it manually. MIM supports multiple fill policies to accommodate traders’ strategies.