What was the Ribbon, and what did Cathy,Mark, and Bryon do there?

The Ribbon is a street full of restaurants and drive-ins. They loiter around, with Mark once randomly punching a stranger in the face who had been crude to Cathy. At their last drive in, tensions between Cathy and Mark reach a head and the two are unable to really speak with each other. Mark goes off on his own to find another friend.