A REALTOR® is a licensed real estate salesperson who belongs to the National Association of REALTORS®, the largest trade group in the country.
Not every agent is a REALTOR®, but most are. If you’re unsure, you can ask your agent if they’re a licensed REALTOR®.
REALTORS® are held to a higher ethical standard than licensed agents and must adhere to a Code of Ethics.
Some REALTORS® are brokers, while some are agents. Unfortunately, people use the term interchangeably: there are some differences.
Brokers are usually managers. They run an agency and have agents working under them as salespeople. They might own a real estate brokerage or manage a franchise operation. They must take additional courses and pay additional fees to maintain their state-issued broker license.
An agent, on the other hand, is a salesperson selling on behalf of the broker.
Agents are also state licensed and must pass a written test before legally acting as a real estate agent. Each state has its own licensing laws and standards.
Some states—like Illinois—have eliminated the real estate salesperson license and mandate all agents take additional course work and pass another test to become brokers. They are broker associates still selling under a managing broker
(source: http://www.realtor.com/advice/what-is-a-realtor/)