The words "bilateral" and "unilateral" are often used in describing offers and contracts. This tutorial concludes by explaining this terminology.
A bilateral contract is one formed by the exchange of promises: the offeror makes a promise and the acceptance is in the form of a promise from the offeror.
A bilateral offer is one that invites or requires a promissory acceptance.
A unilateral contract is one formed by the making of a promise by the offeror and a performance by the offeree in return. In this case, the acceptance takes the form of a performance.
A unilateral offer is one that invites or requires acceptance by performance.