When I post, on the bottom of my post near the plushie and where it says Offline or Online and where it says Scan NYcKiD there is a little gray box with a check and an x in it. If you want to give a rep to some one, you have to click on that gray box with the check and x in it. You get them if some one likes your post and decides you deserve it. It stands for Reputation, so the people that you see that have it green and more than 0 are people who are well known in these forums.