What is the difference between a "Fastpass" and a "Front of the Line" Pass?

You can get a Fastpass at selected rides in the Disneyland Resort and it is free of charge. It basically gives you a later time frame to come back and it holds your place in line so you don't wait as long. 

A "Front of the Line" pass in a theme park such as Univeral Studios, usually has an additional charge, but it gives you exclusive access to areas not usually seen by the public. You also get front of the line privliges for all of the rides.