In Fort, you're a kid! And like many kids, you want to grow your circle of friends, collect pizza and toys, and build the coolest fort.
By doing this cool stuff, you'll score victory points. Your cards not only let you take actions on your own turn, but also let you follow the other players' actions on their turns. Will you devote yourself to your own posse, or copy what the other kids are doing?
Be careful, as your carefully constructed deck might start losing cards if you don't actually use them. After all, if you don't play with your friends, why should they hang out with you anymore?