The document discusses key concepts related to contracts under business law. It defines a contract as an agreement that is enforceable by law. The essential elements of a valid contract are lawful consideration, free consent, lawful agreement, offer and acceptance, contractual capacity, lawful object, possibility of performance, certainty of terms, and legal formality. A void contract is not enforceable by law, while a voidable contract can be enforced or rescinded by one party. Illegal contracts are considered void.