A broker-dealer is a term used in United States financial services regulations. It is a natural person, a company or other organization that trades securities for its own account or on behalf of its customers.
When executing trade orders on behalf of a customer, the institution is said to be acting as a broker. When executing trades for its own account, the institution is said to be acting as a dealer.
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http://en.wikipedia.org/wiki/Broker-dealer
Definition of 'Market Maker'
A broker-dealer firm that accepts the risk of holding a certain number of shares of a particular security in order to facilitate trading in that security. Each market maker competes for customer order flow by displaying buy and sell quotations for a guaranteed number of shares. Once an order is received, the market maker immediately sells from its own inventory or seeks an offsetting order. This process takes place in mere seconds.
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