Just as Oliver Wood gave Harry a crash course in Quidditch, I'll be doing the same here, for any that are new to the sport. I'll also include a bit on brooms.
THE FIELD
The field is oval in shape, with six fifty-foot-high hoops, three at each end. The stands are raised, so the fans can keep up on the action without craning their necks too much.
THE BALLS
There are four balls used in a game of Quidditch. The largest is the Quaffle, a bright red ball. It has no special properties.
Next are the Bludgers. They're like cannonballs. They fly around the field, trying to hit anyone they can.
Last, and smallest...