A contract is an agreement between two parties that creates an obligation to perform (or not perform) a particular duty.A legally enforceable contract requires: 1  An Offer (I’ll mow your lawn this weekend if you pay me $30). 2  An Acceptance (You’ve got a deal). contract is an agreement between two parties that creates an obligation to perform (or not perform) a particular duty. A legally enforceable contract requires: 1  An Offer (I’ll mow your lawn this weekend if you pay me $30).