You have a fake draft where you draft players from whichever team, and then you pick which ones to start weekly. The starters are given points depending on their performance in the game, and then you play someone else in your fantasy league. Whoever has the most points that week wins, and you do that for 16+ weeks.
I rocked the party last week, with 77 points. That put me in second place in my league, though, because someone just so happened to have a great week (read: Donovan McNabb)