Currencies are the official forms of money used by countries or regions to facilitate trade and economic transactions. They act as a medium of exchange, a store of value, and a unit of account. Examples include the U.S. dollar (USD), the euro (EUR), and the Japanese yen (JPY). Currencies can be traded on the foreign exchange market (Forex), where their value fluctuates based on factors like supply and demand, interest rates, and economic stability. Exchange rates between different currencies impact international trade, investment, and economic policies.