Agreements that are entered into and performed by the parties generally fall under the category of contracts. In legal terms, a contract is a binding agreement between two or more parties that is enforceable by law. Contracts can be explicit (written or verbal) or implicit (inferred from actions), and they typically involve the exchange of goods, services, or considerations.
When the terms of the agreement are carried out as intended by the parties, the contract is considered executed. If the obligations set out in the agreement have not yet been performed, it may be classified as executory.
In summary, performed agreements between parties are primarily addressed within contract law.