It depends on the state. In NY we have agents (real estate salespersons) , associate brokers and brokers. An agent and associate broker work under a broker of record who is oversees them, is responsible for handling of funds, supervising them providing them training, etc.. You can only be licensed as an agent or associate broker if you affiliate with a broker (aka brokerage) You can have your own business if you are a broker and also hire agents. Agents and brokers must also take 22 hours of Continuing Education courses and pass exams every couple of years unless they have been a licensed real estate broker for over 15 years.
A broker of record also is entitled to all the commission of a listed property for sale if the list and sell it both or half or a co-broke if they only sell it. If there are agents or associates brokers under the broker involved in a sale there is a split negotiated at hiring
Here is what NYS DOS says:
What is the difference between a real estate broker and a real estate salesperson?
A real estate broker is responsible for the supervision and conduct of the real estate brokerage business. He or she applies for and holds the license on behalf of the brokerage. This person is known as the "representative broker." A real estate salesperson works for and is supervised by the representative broker. The salesperson acts as the representative broker's agent. All listings, although perhaps negotiated by a salesperson, are accepted by the representative broker.
How do I become a real estate salesperson or broker?
Real Estate Salesperson:
In order to qualify for licensure as a real estate salesperson, an applicant must have satisfactorily completed a 75-hour salesperson qualifying education course in real estate approved by the Secretary of State, and have passed a qualifying examination administered by the Department of State. An applicant who completed the 45-hour salesperson qualifying course prior to July 1, 2008 may complete the 30-hour remedial course in order to qualify for licensure.
Real Estate Broker:
In order to qualify for licensure as a real estate broker, an applicant must have at least two years of experience as a licensed real estate salesperson or at least three years of experience in the general real estate field (e.g., buying and selling your own property, managing property owned by your employer), have satisfactorily completed both the qualifying salesperson course of 75 hours and an additional 45-hour real estate broker course as approved by the Secretary of State, and have passed a qualifying examination administered by the Department of State.