A Broker-Dealer (B-D) is a person or corporation that buys and sells securities for their own account or on behalf of their customers. Most stock brokerages in the United States serve as both agents and principals, so the term broker-dealer is used in U.S. securities regulatory jargon to describe them.In order to become a broker-dealer, a firm must first register with the Securities and Exchange Commission (SEC) as a broker-dealer. After registration, the firm must also meet certain net capital requirements, which vary depending on the types of securities the firm deals in.There are a few different types of broker-dealers:-1- full-service broker-dealers2- discount broker-dealers3- combined broker-dealers4- introducing broker-dealers5- holding companiesEach type of broker-dealer has its own set of strengths and weaknesses, so it's important to choose one that's right for your needs.