Google's PageRank is an algorithm used by the search engine to rank web pages in its search results. It evaluates the importance of a page based on the number and quality of links pointing to it. Pages that are linked to by many other high-quality pages are considered more valuable and are ranked higher. The concept behind PageRank is that links act as votes for a page's credibility. Each link contributes to a page's overall score, helping Google determine which pages are most relevant to a user's query. This system helps users find the most trustworthy and useful information online.