This document provides an introduction to international law, including its history, characteristics, models, terms, and meanings. It discusses how international law has developed from governing relations between city-states and individuals in classical times to now regulating relations between modern nation-states and other international organizations. While international law lacks centralized enforcement bodies, it establishes rules that states generally follow in their relations with one another, such as through decisions of international courts and agreements between states. The document explores different perspectives on what constitutes international law.