PageRank is an algorithm developed by Google founders Larry Page and Sergey Brin and plays a key role in the field of search engine optimisation (SEO). Originally introduced to assess the relevance of websites, the term "PageRank" has become an important concept in the world of online marketing.

The PageRank algorithm rates websites based on the number and quality of incoming links. It assumes that a page is more valuable if it is linked to by other high-quality pages. This algorithm has helped to make Google's search results more relevant and to help users find high quality and relevant content.

Although the original PageRank algorithm no longer solely determines Google's search results, it has nevertheless laid the foundation for evaluating the link structure of websites. Today, many different factors play a role in determining search results, including relevance, user experience and content quality. Nevertheless, PageRank remains a fundamental concept for SEO experts who develop link-building strategies to increase the visibility of websites.