Google ranks pages on a basic of PR0 - PR10 A page rank of PR0 is the worst and PR10 is the best. The ranks happen about 4 times a year, so don't worry if you have a lot of PR0's Google uses an algorithm to judge how many backlinks and how credible your page is. People use the Google PR (Page rank) to decide if they are going to buy advertising on somebody's page. I hope this helps.
Page rank isn't the be all and end all though. Look at the site in my sig. It only has a page rank of 3 but currently appears in the no. 1 position in google for Free Money
PR isn't everything, but it measures the strength of your backlinks. Backlinks count for a lot in the search engine rankings, but they aren't everything.
I guess there is no hard and fast table out there that translates PR into number and quality of backlinks.
PR or Page Ranking is an Algorithm developed by Larry Page.If u have high PR the robots crawl ur site more.