-An individual or firm that charges a fee or commission for executing buy and sell orders submitted by an investor.

-The role of a firm when it acts as an agent for a customer and charges the customer a commission for its services.

-A licensed real estate professional, typically representing the seller of a property. A broker's duties may include; determining market values, advertising properties for sale, showing properties to prospective buyers, and advising clients with regard to offers and related matters.  

Traditionally, only the wealthy could afford a broker and access the stock market. However, the Internet triggered an explosion of discount brokers; brokers that let you trade at a smaller fee, but don't provide personalized advice. Because of discount brokers, almost anybody can afford to invest in the market.

Stock-Broker

-An agent that charges a fee or commission for executing buy and sell orders submitted by an investor.

-The firm that acts as an agent for a customer, charging the customer a commission for its services.  

Traditionally, only the wealthy could afford a broker and access the stock market. However, the Internet triggered an explosion of discount brokers; brokers that let you trade at a smaller fee, but don't provide personalized advice. Because of discount brokers, almost anybody can afford to invest in the market.

Dealer

-An individual or firm willing to buy or sell securities for their own account.

-One who purchases goods or services for resale to consumers.   A dealer differs from an agent in that; a dealer acts as a principal in a transaction. That is, a dealer takes ownership of assets and is exposed to inventory risk, while an agent only facilitates a transaction on behalf of a client.

Broker – Dealer

-A person or firm in the business of buying and selling securities operating as both a broker and a dealer depending on the transaction.  

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.

Agent

-An individual or firm that places securities transactions for clients.

-A person licensed by a state to sell insurance.

-A securities salesperson representing a broker-dealer or issuer when selling or trying to sell securities to the investing public.  

Essentially, this is the person who makes a transaction on behalf of his or her employer or client.