A treaty is a formal, legally binding written agreement between actors in international law. It is usually made by and between sovereign states, but can include international organizations, individuals, business entities, and other legal persons. A treaty may also be known as an international agreement, protocol, covenant, convention, pact, or exchange of letters, among other terms. However, only documents that are legally binding on the parties are considered treaties under international law. Treaties vary on the basis of obligations (the extent to which states are bound to the rules), precision (the extent to which the rules are unambiguous), and delegation (the extent to which third parties have authority to interpret, apply and make rules).