The Indian Contract Act 1872 is the main source of law regulating contracts in India. It determines the circumstances in which promises made between contracting parties become legally binding. The Act establishes the essential elements required for a valid contract, including offer and acceptance, lawful consideration, competent parties, free consent, lawful object, and no express voidness. It also defines different types of contracts based on their validity, formation, and performance. The Act aims to enforce the rights and duties of contracting parties under Indian law.