IOC (Immediate or cancel) Immediate or cancel (IOC) orders specify that any part of the order that is not immediately filled must be canceled. Example: You book an IOC order to buy 4 BTC at the price of $40.000, but you can only get 2 BTC at that execution price, you would purchase those 2 BTC, and the rest of the order would be canceled.
FOK ( Fill or kill ) Fill or kill (FOK) orders are either filled immediately, or they are killed (canceled). Example: You book a FOK order to buy 4 BTC at the price of $40.000, it would not partially fill. If the entire order of 4 BTC is not immediately available at that price, the order will be canceled.