A contract that is formed by an exchange of promises by both parties; a promise is made by the offeror in exchange for a promise by the offeree.

A contract that has been completely performed by both parties

A contract that involves a promise by one party and an action/performance of something by the other party. The offer (promise) can only be accepted by the other party’s conduct.

A contract that has not yet been fully performed. Something remains to be done by one or both parties.

A contract in which the terms are stated in words, either written or oral.

A contract that had no validity from the beginning and cannot be enforced by either party. Examples include a contract for an illegal subject or a contract with a serious defect.

A contract whose existence and terms are manifested by the parties conduct, rather than words. The proof of the contract lies in the conduct of the parties.

A contract that possesses all four of the essential elements of a legally enforceable agreement.

An originally valid contract that has been rendered invalid (cannot be carried out) because of a new statute or law that came into existence after the agreement was made.  Another example is a promise made in jest.

A contract that is binding on only one of the parties. The other party has the option to either withdraw from the contract or to move forward to enforce it.

A situation where there is no agreement, no meeting of the minds but one party has rendered a benefit to the other and the rules of fairness will be applied by courts and they will enforce/find this type of contract to avoid unjust enrichment by one party.