[Alneyan]

Hacker should mean someone who knows a lot about how computers actually work, so hackers would be expert Users knowing how to tweak a computer, make a program, and the list goes on. On the other hand, a cracker is someone attempting to break through computers, sites, and so on.

So while hacker usually means "computer literate" (in short, feel free to expand), cracker is more specific to illegal activies. But both words are often mixed, and hacker is used to describe what should be cracking. I am not sure if I make much sense though... *Grumbles*