A written contract serves two important, and related, purposes: It sets out the expectations and obligations of the parties to the agreement and establishes a legal relationship between the parties. The former reduces the possibility of a misunderstanding about who will do what under the contract; the latter allows one party to seek enforcement of the contract in court if there is a breach of the agreement by the other party.

Whether a contract actually accomplishes those purposes depends on how carefully the document is written and whether the language used actually expresses the wishes of the parties. This can be more difficult than it sounds, even when the contract in question is a simple one like a bill of sale