When Cherry and Ponyboy go for popcorn, Cherry asks about Johnny. She has noticed that he is somewhat "twitchy" and nervous. Ponyboy takes to the time to explain that Johnny was once beat up by the Socs. A group of them cornered Johnny is an abandoned lot and beat him so badly that he couldn't move. One guy in particular had these big rings that really did a number of Johnny's face.
Cherry is pale and visibly shaken after Ponyboy's story. She tries to assure him that not all Socs are so violent, but he doesn't believe her. At the same time, the fact that Ponyboy is willing to open up to her so much suggests that he is not as prejudiced against the "other" side as some greasers are. We see that Ponyboy has more of an open mind, and that he might be able to see past the hatred. This scene also sets up the scene after the movie, where Ponyboy will realize that the guy with all the rings is Bob, Cherry's boyfriend.
Two-Bit, Ponyboy and Johnny are the greasers who leave the movie with the girls. They are stopped by a car full of Soc boys, two of whom are Cherry's and Marcia's boyfriends. Things get geared up for a fight, but the girls stop it. When the boys are alone later, however, they will go looking for the greasers that were with their girls, which is the catalyst for the rest of the events in the story.