An agreement differs from a contract in that it doesn’t necessarily have to be in writing. Contracts, on the other hand, must always be in writing, and they must be signed by the parties involved. The fact that it doesn’t have to be written down means that agreements are less binding than contracts and can be terminated more easily.
There are four types of agreements: express, implied-in-fact, implied-in-law, and quasi-contracts.
Express agreements are those made orally or in writing. Implied-in-fact agreements are made through actions or conduct of the parties involved in the agreement; this type of agreement does not have to be written or verbally expressed but is inferred from the actions that took place. Implied-in-law agreements are created by a court to prevent unjust enrichment of one party at the expense of another (i.e., when there is no other way for one party to receive compensation). Quasi-contracts are similar to implied-in-law agreements, except they don’t require a court order; instead, this type of agreement is created when one party benefits from another’s services without compensation. Like delivering food to the wrong address.