You start out with 10 and receive them when you help people. For instance, I could gain a point for answering your question in this thread, if you were kind enough to give me one. Check my sig for more info, or you can view this thread. http://forum.osnn.net/showthread.php?t=3097
Members can only view the number of pips (the green things) another member has got.
You can find out how many points you have by going into the User CP.
Admins/Smods/Mods can go into the Mod CP to see the actual reputation points that a particular member has.