Page rank pretty much means your page popularity on the internet. It infuences stuff like how relevant or how popular is your page on the web and whether you are on top of google results

For instance,
http://theshadling.newgrounds.com/ has a 4/10 PR
http://www.newgrounds.com/ has 6/10 PR
http://eatmeatleet.newgrounds.com/ has 2/10 PR
Go to http://www.prchecker.info/check_page_rank.php and check yourself. If you post a lot you should be steping out of zero soon