The Google PageRank™ is the algorithm that Google uses to determine how important, popular and good a website is and rank it against all other websites. This closely guarded secret is said to be the main reason why Google is one of the most popular search engines in the world.
Amongst many other criteria, PageRank determines the rank of a page by the number and quality of links that point to it. The PageRank score varies from 0 to 10, with the most obscure websites at 0 and the most popular at 10. As you might expect, www.google.com has a rank of 10.
The trademark for PageRank is owned by Google, but it is Stanford University which owns the patent for the technology.