A person or entity that arranges contracts (for real estate, insurance, stocks, and the like)between a buyer and seller for a commission (a percentage of the sales price).For example real estate brokers have the responsibility over an agency and its sales agents as well as their own conduct, insurance brokers is handling more than one company rather than being an agent for just a single carrier, and stockbrokers, who are the upper-level of stock salespersons and/or the operators of brokerage houses. Brokers in many fields are regulated and licensed by each state and have a fiduciary duty to act in the best interests of their customers or clients.