What is the difference between an "insurance broker" and an "agent" and what can they do for me?

What is the difference between an "insurance broker" and an "agent" and what can they do for me?

Elliot Matloff (President and Broker, The Matloff Company) gives expert video advice on: What is the best way to get insurance?; What is the difference between an "insurance broker" and an "agent" and what can they do for me?; What do I do if I have a problem with my agent or broker? and more...