PageRank glossary

http://www.cryer.co.uk/glossary/p/pagerank.htm
PageRank
Refers to Google's "PageRank" algorithm, frequently abbreviated to PR. Google's PageRank algorithm is used by the search engine to score pages based on the number of other pages that link to it and is used to give an indication of the relative importance of a page. Generally speaking pages with a higher page rank will be returned before those with lower page ranks on the search engine's results page (cf SERP). A high PageRank is therefore highly desirable.
The score assigned (or at least the score which is made visible to those outside of Google) is in the range 0 to 10, where 0 is very bad and 10 is extremely high (good). It has been suggested that:
PageRank 0
Often indicates that the page rank has not yet been assigned, or that the site has no inbound links.
PageRank 1 to 2
Very few inbound links, and those links are from low ranking sites.
PageRank 3
Site has some inbound links, either a large number of low quality links or a few links of good quality. Site will be returned on search results, but will tend to be outranked by other competitive sites.
PageRank 4
Site has many good inbound links. An achievable target for most small clubs and companies.
PageRank 5
Site has many good inbound links. Achievable with work. This is the highest PageRank that most sites can realistically aspire to.
PageRank 6
Very difficult to obtain because of the number and quality of inbound links required.
PageRank 7-10
Extremely difficult to obtain for all but the most popular websites. Often only obtained by websites that have become household names.