The European Union is an economic and political union of 27 member states that are located primarily in Europe. It operates as a single market through common policies and by allowing free movement of goods, capital, services, and people between member states. Key EU institutions include the European Commission, which acts as the executive branch, the Council of the European Union, which makes decisions, and the European Parliament, which is elected by EU citizens. 15 member states have also adopted the euro as their common currency. The EU was established after World War 2 to promote cooperation and peace between European countries. It has since grown to include 27 members through several rounds of enlargement.