From The Free Forex Encyclopedia
An agent or company who executes orders to buy and sell currencies and related instruments for their clients; they typically make money on either the commission or on a spread. Brokers are agents working on commission and not principals or agents acting on their own account.
In the foreign exchange market, brokers tend to act as intermediaries between banks bringing buyers and sellers together for a commission paid by the initiator or by both parties. There are four or five global brokers operating through subsidiaries, affiliates, and partners in many countries.