Treaties are international agreements between nations. They are sometimes called conventions, declarations, accords, or protocols, etc.Treaties can be bilateral, meaning that they apply only to two countries, or multilateral, meaning several countries..
Here are some online sources.
You can also find treaties in subscription databases (HeinOnline, Lexis and Westlaw), in print series (in the Law Library at and around KC10), and often also in relevant textbooks.
Look online for the Minisitry of Foreign Affairs (or equivalent) for up to date treaty information on the country or countries you are interested in.