Forex, or foreign exchange, refers to the global marketplace for trading national currencies against one another. It involves buying one currency while simultaneously selling another, and it is the largest and most liquid financial market in the world. Forex trading allows individuals, banks, corporations, and governments to exchange currencies and speculate on currency exchange rates. Traders use the forex market for various purposes like international trade, investment, hedging, or simply to take advantage of currency fluctuations to make profits.