Anyone who earns a real estate license can be called a real estate agent, whether that license is as a sales professional, an associate broker or a broker. State requirements vary, but all require a minimum number of classes and pass a test to earn your license.
A REALTOR is a real estate agent who is also a member of the National Association of Realtors.
A Broker is a person who has taken education beyond the agent level as required by state laws and has passed a broker’s license exam. Brokers can work alone or they can hire agents to work for them.
An Associate Broker has taken the education course and passed the broker's license exam but is not working as the designated broker of a real estate agency at this time.
Hopefully this clears up some of your confusion.