This document provides an overview of political science and the concepts of state and government. It discusses that political science is the study of the state, government and politics. It also examines the key elements of a state including territory, people, government and sovereignty. Several theories on the origin of states are outlined such as the divine right theory, necessity theory and social contract theory. The main purposes of government are then defined as defense, national identity, representation, infrastructure and social welfare. Finally, the principal forms of government are categorized based on the number exercising power, the extent of central government authority, and the relationship between executive and legislative branches.