The notion that a hacker is this nerdy geek who sits behind his computer for days on end is, although not far off, is pretty much incorrect. The general populous might imagine these almost alien like figures of computing culture to be on a vindictive, vandalistic course of destruction as a result of some sort of troublesome childhood.
Technically this may all be vaguely correct but generally there is very little known about this tech sub-culture that has been around for, well, as long as the computer itself. Generally speaking hackers are the good guys. They are against monopolies, dictatorship and censorship and tend to have a very good sense of what's right and wrong without having any political agendas. But, as with anything good and pure, there are the bad apples.