A stockbroker is a regulated professional individual, usually associated with a brokerage firm or broker-dealer, who buys and sells stocks and other securities for both retail and institutional clients, through a stock exchange or over the counter, in return for a fee or commission. Stockbrokers are known by numerous professional designations, depending on the license they hold, the type of securities they sell, or the services they provide. In the United States, a stockbroker must pass both the Series 7 and either the Series 63 or the Series 66 exams in order to be properly licensed.