Forex, or the foreign exchange market (also called FX for short) is the marketplace where currencies are traded. At its simplest, a foreign exchange transaction might be, for example, when you transfer your local currency to a new one for an upcoming holiday. Across the market as a whole, an estimated 5.3 billion USD is traded every day between governments, banks, corporations, and speculators.
Currency trading and exchange first occurred in ancient times. Money-changers (people helping others to change money and also taking a commission or charging a fee) were living in the Holy Land in the times of the Talmudic writings (Biblical times). These people (sometimes called "kollybistẻs") used city stalls, and at feast times the Temple's Court of the Gentiles instead. Money-changers were also the silversmiths and/or goldsmiths of more recent ancient times.
One unique aspect of this international market is that there is no central marketplace for foreign exchange. Rather, currency trading is conducted electronically over-the-counter (OTC), which means that all transactions occur via computer networks between traders around the world, rather than on one centralized exchange. The market is open 24 hours a day, five and a half days a week, and currencies are traded worldwide in the major financial centers of London, New York, Tokyo, Zurich, Frankfurt, Hong Kong, Singapore, Paris and Sydney—across almost every time zone. This means that when the trading day in the U.S. ends, the forex market begins anew in Tokyo and Hong Kong. As such, the forex market can be extremely active any time of the day, with price quotes changing constantly.