Speed is a game played with a standard fifty-two card deck that relies on quick thinking and reflexes. The goal of the game is to get rid of all your cards first as quickly as possible — this makes it part of the "shedding" family of card games. If you really like this game, you can also play "Spit," which is a similar shedding card game with more complicated rules.
If you want a more "written" out explanation of the game you can see here.