A currency is a system of money that is used as a medium of exchange for goods and services. It can be in the form of physical coins and banknotes or digital money. Different countries have their own currencies, such as the US Dollar, Euro, and Japanese Yen, which can vary in value based on economic factors. Currencies are traded in foreign exchange markets, where their values fluctuate based on supply and demand. Exchange rates determine how much one currency is worth in relation to another, influencing international trade and travel. Understanding currencies is essential for global commerce and economic stability.