The foreign exchange market (currency, forex, or FX) trades currencies. It lets banks and other institutions easily buy and sell currencies.
The purpose of the foreign exchange market is to help international trade and investment. A foreign exchange market helps businesses convert one currency to another. For example, it permits a U.S. business to import European goods and pay Euros, even though the business's income is in U.S. dollars.
In a typical foreign exchange transaction a party purchases a quantity of one currency by paying a quantity of another currency. The modern foreign exchange market started forming during the 1970s when countries gradually switched to floating exchange rates from the previous exchange rate regime, which remained fixed as per the Bretton Woods system.
The foreign exchange market is unique because of

• its trading volumes,
• the extreme liquidity of the market,
• its geographical dispersion,
• its long trading hours: 24 hours a day except on weekends (from 22:00 UTC on Sunday until 22:00 UTC Friday),
• the variety of factors that affect exchange rates.
• the low margins of profit compared with other markets of fixed income (but profits can be high due to very large trading volumes)
• the use of leverage

Main foreign exchange market turnover, 1988 - 2007, measured in billions of USD.

As such, it has been referred to as the market closest to the ideal perfect competition, notwithstanding market manipulation by central banks. According to the Bank for International Settlements, average daily turnover in global foreign exchange markets is estimated at $3.98 trillion. Trading in the world's main financial markets accounted for $3.21 trillion of this. This approximately $3.21 trillion in main foreign exchange market turnover was broken down as follows:

• $1.005 trillion in spot transactions
• $362 billion in outright forwards
• $1.714 trillion in foreign exchange swaps
• $129 billion estimated gaps in reporting