Sometimes contract law doesn't provide adequate relief. For example, A may intend to send B money, but by mistake sends it to C. A can't recover from C under contract law because there is no contract. Or A may provide services to B without any agreement from B to compensate A. In both those situations, since A doesn't have a contract, he can't claim breach of contract.
So the law has supplemented contract law with principles to alleviate the harsh results of applying only contract law. They're called equitable remedies or equitable relief. The equitable remedies are described in the sub-practice pages.