That sure is a can of worms..
Yes, Page Rank (Google) is supposed to be how popular your site is and is considered to be a view of how many important sites ‘vote’ for you.
For example, if a PR7 site has a link to you on their site.. It is considered a ‘vote’ for your site. It is an important ‘vote’ because they have a high PR (which is good). If a PR1 site ‘votes’ for you (puts up a link to your site), it does not have the weight of the PR7 link.
PR, imho, means very little…. Unless, of course, you want someone to ‘vote’ for you by putting up a link. Then…. it means just about everything – unless you have cash to pay for your links.
Hope that helps.
PS – I think toolbar.google.com will get you the toolbar that shows page rank for the Firefox browser. Search Google for the IE version.