The market in which participants are able to buy, sell, exchange and speculate on currencies. The forex markets is made up of banks, commercial companies, central banks, investment management firms, hedge funds, and retail forex brokers and investors. The currency market is considered to be the largest financial market in the world, processing trillions of dollars worth of transactions each day.The foreign exchange markets isn't dominated by a single market exchange, but involves a global network of computers and brokers from around the world. Central banks use their massive buying and selling capabilities to alter exchange rates through their open market activities and in many cases will do so not with profit in mind, but rather for any number of policy reasons. Forex brokers act as market makers as well, and may post bid and ask prices for a currency pair that differs from the most competitive bid in the market.