Each writeup (user-posted node) has a numeric reputation, which is a (very unreliable) indicator of the PerlMonks community's collective estimation of the writeup. A writeup's reputation is simply the sum of the up-votes and down-votes which that node has received. So, for example, if 5 monks voted ++ on a node and 3 other monks voted -- on it, then that node's reputation would be 2.
Please remember that only nodes have a quantitative reputation; users do not. Each registered monk has experience points, a distinct quantity which is determined, only in part, from the up-votes and down-votes which his/her writeups have received. Read Voting/Experience System for the gory details.
(Of course, everyone has real reputation and real experience, but PerlMonks makes no attempt to quantify these. :-)