If someone likes one of your posts they click a little button that looks like this . They click approve or disapprove, which adds or subtracts reputation points (like said above, these can be viewed from your User CP) and your "e-penis" grows or shrinks.
when I opened I thought this was going to be about xanax.. and I've never even done it. Oh, what reading Pandora's Box posts has done to my mind! My e-peeniz is growing too! Like most of the other people here, it compensates for my real life penis! Neat-o!