A contract is a promise or a set of promises for the breach of which the law gives a remedy, or for the performance of which the law in some way recognizes a duty.
Good Faith - UCC
Every contract or duty has an obligation of good faith; failure to perform in good faith is breach of contract.
Good Faith - CL
Implied covenant of good faith and fair dealing with every contract.
Breach
Failure or refusal to perform under a binding contract without valid legal excuse