Currencies are systems of money used in different countries to facilitate trade and economic transactions. They can be physical, like coins and banknotes, or digital, like cryptocurrencies. Each currency has a specific value and is often represented by a unique symbol, such as the US Dollar ($) or the Euro (€). The value of a currency can fluctuate based on various factors, including economic stability, interest rates, and inflation. Countries may exchange their currencies in the foreign exchange market, where traders buy and sell currencies to profit from these changes. This exchange is essential for international trade and travel.