It shows the number of violent crimes in the US by year, from 1973 - 2005, then parallels it with video games.
I've reproduced it here (it's kinda wide, so I made it a spoiler)
[spoil]

Basically... it says that blaming video games and music for violent acts is a bunch of horse shit. End of story.
I've included a few "violent" video games and a Marilyn Manson album in the timeline. You can view the raw data and more at the U.S. Department of Justice's website (specifically on this page).