An offer is a definite, clear, and final proposition made by an offeror to an offeree with the intention of being legally bound if the offeree accepts it. Once an offer is accepted, it creates a binding contract. Examples include a promise to sell goods at a specific price.

An invitation to treat, on the other hand, is merely an invitation to negotiate or to make an offer. It is not binding on the person making the invitation and is meant to encourage offers. Examples of invitations to treat include advertisements, shop window displays, and auction notices.