A contract is defined as an agreement that is enforceable by law. The key elements of a valid contract are an offer, acceptance of that offer, lawful consideration, lawful object, and mutual consent between competent parties. Not all agreements are considered contracts - an agreement must meet additional requirements of enforceability and intention to create legal obligations to be a valid contract. Common types of agreements discussed include valid contracts, void agreements, voidable agreements, and invitations to treat which are not considered offers. Key aspects of forming a valid contract center around offer, acceptance, and consideration.