Time In Force

This determines how your order will be executed on the exchange.

Fill or Kill

A fill or kill order will try to buy/sell at the given price, but will cancel and trade nothing if it cannot get the full desired quantity.

There will be no resting order that can execute at a later time.

Immediate or Cancel

A immediate or cancel order will try to buy/sell at the given price, but will trade as much as it can get, which might result in a partial fill less than the desired quantity.

There will be no resting order that can execute at a later time.

Day

A day order may trade immediately depending on market conditions, but otherwise will remain on the order book and potentially finish executing later if the markets change.

Day orders are cancelled at the end of the day, as described by CME market schedules.