PageRank: PageRank, or PR, is an algorithm developed by Google founders Larry Page and Sergey Brin during their time at Stanford. Ostensibly a quality marker, it measures a website’s “importance” within a grouping of related pages.
A website can be ranked on a scale of 0 to 10, with 10 indicating the most important pages in that set. Ranks are determined by the links leading to a site, assuming that since people share relevant and high-quality content, linking to a site indicates its importance. The system gives more weight to links that come, in turn, from more important websites. This is intended to prevent people from boosting their ranking through link farming or Google bombs. A Google bomb is when a group of people artificially associate a webpage with a certain keyword such that the site appears high in the results when the keyword is searched.
Page rank tools allow users to check the ranking of their page, as well as the factors contributing to that rating. Experts disagree on the extent to which PageRank influences a website’s SEO ranking for any particular keyword, since search engines want to offer relevant results to their users, which may or may not correspond with "important" pages.
Despite potentially being part of, or determined by some of the same factors as, the complex algorithms that rank search results on Google’s search pages, the name likely comes from Page’s last name.