Most times, a well-written contract will include a list of things that will breach the contract. If you ever need to know what terms break the contract, you should look first to the contract that you signed. There will likely be several clauses on breaches.
If the terms are not explicit, there are some general things that will breach a contract. For an employment contract for an actor or actress, the actor or actress will commit to temporary employment for as long as the project takes. If that project is a play, for instance, refusal to perform in the play, missing performances, or accepting a role in another play is a breach of contract.
For mortgages or other personal loans, a breach can occur if you stop making payments during a repayment period. The economic crises of the last few years have made it difficult to repay loans on time. If you meet with your loan provider to discuss or refinance a loan, it does not put your loan in breach of contract. This simply allows the parties to a contract the ability to renegotiate the terms of the contract.
Parties to a contract can always agree to either relieve the other of the terms of the contract or cancel the contract the contract altogether. A breach occurs when only one party to the contract decides to stop performing according to the terms of the contract.