It is...an extremely rough but very popular semi-contact sport played by wizards and witches around the world. Matches are played between two teams of seven players riding flying broomsticks, using four balls and six elevated ring-shaped goals. In the Harry Potter universe, Quidditch holds a fervent following similar to football (soccer) as a globally popular sport. [Wikipedia]Since the intercollegiate teams don't have access to flying broomsticks or other magical devices, they play a variant called Muggle Quidditch that is adapted for the non-magical world. The first intercollegiate match took place in 2007, between Middlebury and Vassar Colleges (some photos here).
On one hand, I'm like "NERD ALERT!" On the other, the students look like they're having fun, so who am I to judge that? Here's a "trailer" for intercollegiate Quidditch: