A Broker

An auto transport broker is a company who has the authority through the US DOT to act as a middle man between customers and carriers.  A broker company will come in contact with a customer who is looking to transport their car (either from their own website, purchase leads, or possibly through a referral).  The reason the auto transport industry is so broker reliant is because over 90% of truckers out there on the roads are owner operators and usually stick to a specific route or geographic location; they are not nationwide companies.  Brokers are able to post a vehicle or call a company that they know who does the exact route the customer is requesting.  A customer will normally be signing a contract to work with the broker company and in turn the broker company signs a contract with the carrier to perforem the transport.

A Carrier

A carrier is the actual company that performs the transport of your vehicle.  As mentioned above, they are usually the owner operator of the business and normally only concentrate their efforts to 1 route or geographic location.  The carrier is the one who will have the proper insurance the covers your vehicle during the transport as well.

As a customer your first communication will be with a broker.  Once the broker finds the hauler to perform your transport requst you'll have the cariiers information as well.  Still, your main point of contact should be the broker who your contract is with.