A real estate broker is a party (individual or an agency) who acts as an intermediary between sellers and buyers of real estate. They are proactive in their work as they attempt to find sellers who wish to sell and buyers who wish to buy. In the United States, the relationship was originally established by reference to the English common law of agency with the broker having a fiduciary relationship with his clients.

In the US, real estate brokers and their salespersons (commonly called "real estate agents") can wear two hats depending on if their client is the seller or the buyer. They assist sellers in marketing their property and selling it for the highest possible price under the best terms. When acting as a Buyer's agent with a signed agreement (or, in many cases, verbal agreement), they assist buyers by helping them purchase property for the lowest possible price under the best terms. Without a signed agreement, brokers may assist buyers in the acquisition of property but still represent the seller and the seller's interests.

In most jurisdictions in the United States, a person is required to have a license in order to receive remuneration for services rendered as a real estate broker. Unlicensed activity is illegal, but buyers and sellers acting as principals in the sale or purchase of real estate are not required to be licensed. In some states, lawyers are allowed to handle real estate sales for compensation without being licensed as brokers or agents.

The difference between salespersons and brokers

In the past, when brokers (and their agents) only represented sellers, the term ‘’real estate salesperson’’ may have been more appropriate than it is today, given the different ways that brokers and their agents can help a buyer through the process rather than simply “sell’’ him or her a property. Legally however, the term 'salesperson' is still used in many states to describe a real estate agent.

Real estate education: In order to become licensed, most states require that an applicant take a minimum number of classes before taking the state licensing exam. Such education is often provided by real estate brokerages as a means to finding new agents.

Today in many states, the real estate agent (acting as an agent of the broker with whom he/she is employed) is required to disclose to prospective buyers and sellers who represents whom. See below for a broker/agent’s relationship to sellers and their relationship to buyers.

While some people may refer to any licensed real estate agent as a real estate broker, a licensed real estate agent is a professional who has obtained either a real estate salesperson's license or a real estate broker's license.

In the United States, there are commonly two levels of real estate professionals licensed by the individual states, but not by the federal government:

Real estate salesperson: When a person first becomes licensed to become a real estate agent, he/she obtains a real estate salesperson's license from the state in which he/she will practice. To obtain a real estate license, the candidate must take specific coursework (of between 40 and 90 hours) and then pass a state exam on real estate law and practice. In order to work, salespersons must then be associated with (and act under the authority of) a real estate broker.

Many states also have reciprocal agreements with other states, allowing a licensed individual from a qualified state to take the second state's exam without completing the course requirements, or, in some cases, take only a state law exam.

Real estate broker: After gaining some years of experience in real estate sales, a salesperson may decide to become licensed as a real estate broker. Commonly more course work and a broker's state exam on real estate law must be passed. Upon obtaining a broker's license, a real estate agent may continue to work for another broker in a similar capacity as before (often referred to as a broker associate or associate broker) or take charge of his/her own brokerage and hire other salespersons (or broker) licensees.

Becoming a branch office manager may or may not require a broker's license. Some states such as New York allow licensed attorneys to become real estate brokers without taking any exam. In states, such as Colorado, there are no "salespeople", as all licensees are Brokers.