Yeah, Enterprise was a prototype. It basically tested how the Shuttle design would fly in the atmosphere. Columbia was the first space going Shuttle.
Interesting fact is that after the Challenger disaster, they considered retrofitting Enterprise for space flight. But, they deemed it cheaper to take spare parts from Discovery's and Atlantis's construction to build Endeavour.
That's cool, it's strange how this and Concorde existed and then not really taken any further.
Here's my last contribution of Enterprise: http://youtu.be/Lx8mxUO8DMM
Recorded on my Sony A55, then uploaded from the iPad, which was good to do, but I would need some more space.