The heart of Google search algorithm is PageRank, a system for ranking web pages. Though engineers at Googleplex are working hard to improve every aspect of Google on a daily basis, PageRank continues to provide the basis for all of their web search tools.
To put it in short, Google use PageRank to determine a page's relevance or importance.
Our PageRank Tool will query and return the Google PageRank values for submitted URL from various Google datacenters. Usually all returned values are the same, but when there's an update going on, you will be able to watch out your Page Ranks closely.