Karma

Karma points are nothing but how much you are popular and helpful on the forums. If some one really like your presence here and wanted to give thumbs up, he can do that and your karma increases and if he dont like, he will thumbs down.

There is nothing more than that

I don't think many of the new users(also the old users) don't notice the karma thing, since it is too small to notice, I think people will notice it if the karma (thumbs up/down) is near the profile avatar or near the topic itself,rather than in one corner(not many of the users get thumbs up or even the thumbs down!! :-( )