What is SEO Page Rank?

'PageRank' is the name Google has given to a formula it uses to assign relative importance to any given page on the web. The higher the pagerank, the more important the page.

Popular sites such as Wikipedia and BBC tend to have high page rank (7 or more). Brand new sites start with a pagerank of zero.

One method of improving a site's performance in Google is to increase its pagerank. It's worth noting that Google place greater emphasis on page content, and that pagerank is merely one of several factors in the struggle for SEO supremacy.

Pagerank tends to be earned via external links into a site from a third party.

A link from a page with a high pagerank will convey much more 'link juice' than one from a site with low pagerank. This is why SEO professionals work hard on both building pagerank of sites under their direct control, and getting links in from sites with high pagerank.

Of course, an inbound link will work even better in terms of Google performance for a particular keyword if its contextual. It's worth remembering that pagerank isn't the only factor, and focussing on it to the exclusion of all else won't necessarily help a site perform well in Google.