A person or firm in the business of buying and selling securities operating as both a broker and a dealer depending on the transaction.
Investopedia Says:
Technically, a broker is only an agent who executes orders on behalf of clients, whereas a dealer acts as a principal and trades for his or her own account. Because most brokerages act as both brokers and principals, the term broker-dealer is commonly used to describe them.
Related Links:
If you want professional advice and commission-free trading, this may be the way to go. Introduction To Fee-Based Brokerage Accounts
How do you find the right broker for your investment needs? Start by reading our broker tutorial. Brokers and Online Trading
Knowing how the primary and secondary markets work is key to understanding how stocks trade. Markets Demystified


