An order is a request that you have sent to the exchange. Your order may or may not be matched to a counter-party. You do not contribute collateral unless your order is matched. If there is no matching counter-party, your order will sit and wait. When the option expires, your order will expire as well. You are free to cancel any open order at any time before it is matched into a contract.

When your order is matched to another party, a contract is created. both sides are charged their respective collateral. When the option expires, the winning party receives the payout. You may not cancel a contract, as it is a binding agreement between the two parties.