What is a contract? More than just an idle or gratuitous promise, a contract arises at law when two or more persons agree to bind themselves to mutual legal obligations by an exchange of “consideration,” or things of value. These things might be performing tasks, providing personal property, or agreeing to provide these things once one or more conditions are met. While parties do not usually have to put a contract in writing for a court to enforce a contract, usually it is a good idea. Here are some simple reasons why.