PageRank relies on the uniquely democratic nature of the web by using its vast link structure as an indicator of an individual pageis 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."
Important, high-quality sites receive a higher PageRank, which Google remembers each time it conducts a search. Of course, important pages mean nothing to you if they donit match your query. So, Google combines PageRank with sophisticated text-matching techniques to find pages that are both important and relevant to your search. Google goes far beyond the number of times a term appears on a page and examines all aspects of the pageis content (and the content of the pages linking to it) to determine if itis a good match for your query.
One Observer, Vince Tourangeau, pointed out that interestingly, but perhaps not surprisingly, a search for "X" on Google returns Appleis Mac OS X page as one of the top few links. Appleis new OS is drawing more attention than such other famous Xis as The X-Files, X Windows, and The X-Men.
You can search for X yourself at the Google Web site, and find more information about Mac OS X at the Apple Web site.