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 in all states you must take a minimum number of classes and pass a test to earn your license. Real estate 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.

A real estate agent must work for an broker and cannot work independently Whereas Brokers are responsible for their real estate agents’ actions.
Real estate agents often do the same work as brokers, but they aren’t qualified to run their own firm.

Or Simply we can say that agents work directly for brokers and can only practice real estate under the supervision of a broker. Agents cannot work independently or open a real estate brokerage.