An Insurance Broker is someone/entity who represents you with your insurance transactions, unlike an insurance agent, who only represents the insurance company.
An insurance broker is an independent insurance agent who works with many insurance companies to find the very best available policies for his or her clients.
A typical insurance agent works for one specific company, and chooses from within that company's policies for clients. While an insurance broker is different from the typical agent in this regard, the two are otherwise similar. Both usually work on a commission basis.