Moderation!

I'll move this topic to the  correct place sinse Socheat is right, this is about the forum.
Socheat is also correct that the Site and forum faq explains all about User    Karma as well as many other things.

To give a brief answer, User Karma is like public reputation. When someone writes a post you like, you can use the "thumbs up" link at the bottom of the post to give the person another point of karma. Whether it's because they've been funny, or informative or helpful or whatever. The more thumbs ups someone gets, the more there karma.

it's not really something to be taken too seriously, just a way of saying "hay I like that post" 

Hope this makes sense.