What is Google PageRank?
Google assigns each web page a PageRank between 0 and 10, The PageRank is a measure of the weight or importance Google gives the web page: 0 is the lowest importance and 10 the highest.
Here is Google’s definition of PageRank:
PageRank relies on the uniquely democratic nature of the web by using its vast link structure as an indicator of an individual page’s value. In essence, Google interprets a link from page A to page B as a vote, by page A, for page B. But, Google looks at more than the sheer volume of votes, or links a page receives; it also analyzes the page that casts the vote. Votes cast by pages that are themselves “important” weigh more heavily and help to make other pages “important”.
Put simply, the more hyperlinks there are to a page the more important Google considers a page. Links from important pages count for more than links from less important pages.
In theory, if two web pages contain the words “mysterious algorithm” and a user searches for this on Google, the page with the higher pagerank will appear higher in the search results.
Historically, Google’s algorithm for assigning a rank to a web page was what distinguished the Google search engine from others such as Yahoo or Alta Vista. Google’s algorithm allowed the rapidly growing number of web pages on the internet to be catalogued and ranked making searches more meaningful to users. In more recent years though, Google has increasingly modified its ranking algorithm to be biased toward to content of webpages rather than the incoming links.
For more information, see PageRank on Wikipedia.