The Confundus charm confuses the opponents. It turns around the screen and reverses the controls, making it very difficult to move around. Many players choose to stand still during the Confundus Charm. It stays active for 5 seconds.
From the Story
Discovered in Book 3, Chapter 21 Hermione's Secret
"Professor Snape tells Cornelius Fudge that Sirius Black must have used the Confundus Charm on Ron, Harry and Hermione, which accounts for their belief in his innocence."
Discovered in Book 4, Chapter 17, The Four Champions
"Alastor Moody says that it would have taken an exceptionally strong Confundus Charm to bamboozle the Goblet of Fire into forgetting how many schools compete in the Triwizard Tournament."