This document provides an introduction to the field of international relations. It discusses what international relations concerns, which is the relationships among the world's governments. It also explores what career paths one could pursue by studying international relations. The document outlines the four sets of relations within the sphere of international relations: relations between states, relations between societies, state-society relations within countries, and state-society relations across borders. It then discusses three core principles of international relations - dominance, reciprocity, and identity - and how they relate to solving collective action problems between groups.