Agent

One authorized to represent and to act on behalf of another person (called the principal). Unlike an employee, who merely works for a principal, an agent works in the place of a principal. The main difference between an agent and an employee is that agent may bind the principal by contract, if within the scope of authority, whereas an employee may not unless given express authorization. 

A real estate broker is the agent of the client (seller or buyer) to whom she owes a fiduciary or statutory obligation. A salesperson, on the other hand, is the agent of his broker and does not have a direct personal contractual relationship with either the seller or the buyer. This fact is relevant when a salesperson decides to change firms and becomes upset when the broker won’t let the salesperson take his listings. 

Note that minors cannot appoint an agent to execute their contracts, but an adult may designate a minor to act as an agent.