Google Information
PageRank™ or PR is Google's patented method to determine a page's relevance and importance through the quality & quantity of sites linking to it. PR is a unique algorithm for assigning numerical weightages to hyperlinked documents, primarily web pages, - indexed by the search engine Google. The main factor behind the PageRank algorithm is link popularity. If one site links to another site, then Google interprets this link as a vote. The more votes cast, the more importance the page is considered to be possessing from Google's point of view, - in terms of any specific issue/content.
A score out of ten is assigned by Google to each indexed web page. The 'Green Bar' is the visible result of the algorithm, displayed on a scale from 0 - 10, where 10 is the highest.
Your Google page index is simply the number of pages from your website that Google has in its database (index).
Googlebot is Google's web crawling robot, which finds and retrieves pages on the web and hands them off to the Google indexer. Google adds and update new sites to its index each time it crawl the web.