PageRank (PR) is a mathematical equation based on the number of times Google’s indexing applications will find links to your site on 2 complete crawls of its entire index. Years ago this was the primary method Google used to rank web sites… the more links, the higher your rank.
Of course SEO people got wise to this and very quickly had tons of links pointing to their sites, so Google had to adjust its algorithm. Today a PageRank 1 web site can out rank a PageRank 5!
Is PR still Important?
So is PageRank still important? Yes, although it is not used exclusively to list web sites, PageRank is still important because the number of pages that Google will crawl on your site is proportional to your PageRank. A PR 7 site can have 10s of thousands of pages in Google’s index (See Amazon.com) while a PR 2 might only get a few listed.
This means sites with little or no PageRank will not have much of a chance of getting their interior pages regularly crawled. No crawls means no ranks for thoise pages. So PageRank may not be in Google’s ranking algorithm any longer, but if you want your interior pages to be considered for ranking, you should pay attention to it.