Treaties are the most important source of international law and may be referred to by many names, including but not limited to, convention, agreement, pact, or accord. A treaty is an agreement between countries and/or international organizations. Treaties can be either bilateral (between two countries or international organizations) or multilateral (between three or more countries or international organizations).
In the United States, a distinction is made between treaties and executive agreements. The term "treaty" is reserved for an international agreement that has entered into force after receiving the advice and consent of the Senate pursuant to Article II, Section 2, Clause 2. All other international agreements are considered "executive agreements." For the sake of simplicity, this research guide will use the term "treaty" to refer to all international agreements, whether they are "advice and consent" treaties or not.
You will likely encounter unfamiliar terms when conducting treaty research. Understanding the terminology is essential for understanding a country's obligations under the treaty. For instance, a reservation is a limitation on a state's commitment, i.e., a condition on its consent to be bound by the treaty.
A glossary of terms relating to treaty actions is available on the UN Treaty Collection's website here.