A broker-dealer is a financial professional or firm that buys and sells securities, such as stocks and bonds, on behalf of clients or for its own account. They act as intermediaries in the financial markets, facilitating transactions between buyers and sellers. Broker-dealers can provide various services, including investment advice, market research, and portfolio management. There are two main types of broker-dealers: full-service broker-dealers, which offer a wide range of services and personalized advice, and discount broker-dealers, which provide fewer services at lower costs. Both types play a crucial role in ensuring liquidity and efficiency in the financial markets.