An acceptance is not an acceptance if changes the terms of the offer. A contract is an agreement between two parties that creates an obligation to perform (or not perform) a particular duty.An offer is a proposal from one party to another intending to create a legal obligation upon acceptance. ) (agreement. Acceptance. Under Texas law, to prove a valid acceptance of an offer, a party must show: • The acceptance was made before the offer lapsed or. A contract is simply a promise between two parties that can be legally enforced. Offer and acceptance. An offer is a clear intention to enter into a legally binding agreement. It marks the first step in creating that agreement.