This document provides an introduction to concepts in international relations including what international relations studies, definitions of key terms like country, state, sovereignty, and nation-state. It also summarizes different approaches to foreign policy like isolationism vs internationalism and tools of foreign policy such as diplomacy, alliances, trade, foreign aid, and sanctions. Current world trends are outlined as growing interdependence, US influence declining and rise of other powers, spread of democracy and technology. National interests and how they drive foreign policy decisions are also explained.