This document provides an introduction to the law of contract. It defines a contract as a legally binding agreement that can be enforced in courts. Contracts are classified as contracts by deed, which are formal legal documents, or simple contracts, which can be written, oral, or implied. Contracts are also classified as bilateral, involving promises exchanged between two parties, or unilateral, involving one promise in exchange for an act. The essential elements of a valid contract are agreement between the parties, consideration, intention to create legal relations, required form, capacity to contract, consent, and legality of purpose. Contracts can be void, voidable, or unenforceable depending on defects that impact validity or enforceability.