They're reputation points. You'll notice a green up-arrow to the right side of every post, that's where these points come from. I think the idea is the help sort out the more reputable users. When you read posts that deserve two-thumbs up, give em a point. Hold your curser on someone's user name, and a little box will show up, showing their reputation points and how many posts that person has. If they've made a lot of posts, and don't have any rep. points.... they might just be full of crap, or stirring up crap!! LOL IMO, that's how it supposed to work... Should be a down arrow as well though!