It is mainly used to optimize the website. It is refers to the pages that can be loaded via multiple URLs. This is a issue that fades out the link popularity.

Long time quality of the site can only increase the PR Of the site. I can never of sudden change. Try to generate quality links from high PR sites. Also, create quality unique content in the site that is beneficial to the readers.

Bruce Clay is the Father of SEO, as he only coined the term.