Offer is an expression of willingness with intention to become legally bound when accepted. An offer may be made to the public and becomes a binding contract upon acceptance. An offer is not an invitation to treat or negotiate. Key elements of a valid offer include it being communicated to the offeree and having the intention to create legal relations upon acceptance. Common exceptions to offers being made include advertisements, displays of goods with prices, and auctions which are usually considered invitations to treat rather than binding offers. An offer can be withdrawn or lapse due to time or conditions not being met before acceptance.