In addition to terms that become part of a contract by agreement, terms can be made part of the contract by operation of law. These are sometimes referred to as 'terms implied by law' or 'terms imposed by law'.
The law makes certain terms part of every contract: these are called 'universal terms'.
The law makes certain terms part of particular kinds of contract: these are called 'generic terms'.
If a term is put into a contract by operation of law, it creates obligations and becomes enforceable in the same way as agreed terms.