The foreign exchange market, also known as FX or Forex trading, is a global decentralized or over-the-counter (OTC) market for the trading of currencies. It is by far the largest market in the world (Forex trading surpasses $4.9 trillion daily), followed by the credit market.
Unlike some other markets, this is no central market for Forex trading. Currency trading is all done over the counter electronically on global computer networks between individual traders. There are five major Forex trading centers: Frankfurt, Hong Kong, London, New York and Tokyo.
The Forex market is open 24 hours a day, five and a half days a week, and operates across nearly every time zone, which makes for an active market in a continual state of flux, with prices changing all the time.