What IS the difference between Crysis and Crysis Warhead?

Is Crysis Warhead just a multi-player game, or does it have the story AND multi-player?



Because the only one I have seen in stores is Crysis Warhead and from what I have heard it is just multi-player, and I don't care much for multi-player fps's on my slow internet connection.



Also many places stated that it was an "expansion pack," so does that mean that I need both? or is it just a sequel?What IS the difference between Crysis and Crysis Warhead?
check this article out and you will find the difference

http://pc.ign.com/objects/142/14258182.html