PageRank is the Google trademark which is named after company co-founder Larry Page and represented in the number form 0-10. Up the scale websites are considered as better ones than the websites having value assigned as down the scale.
As Google says “PageRank works by counting the number and quality of links to a page to determine a rough estimate of how important the website is. The underlying assumption is that more important websites are likely to receive more links from other websites.”
It is believed to be calculated on a logarithmic scale as PR(P)= PR(Q) + PR(R) + PR(S)
The Toolbar Page Rank has a less impact on search engine ranking where as it is believed that Google keeps an internal record of Page Rank which has bigger impact on the performance of the websites in SERP.
The PageRank is not an absolute measure of any website rather it counts the quality back links pointing towards a site and a pagerank value is assigned according.
It represents how well your website ranks in terms of Google pagerank algorithm which is different form ranking algorithm and probably is the only expression where Google represent the importance of a site by numeric values.
Content and bad links are not taken into account when calculating the PageRank. Content updates do not improve the pagerank. The page rank is a recursive procedure of calculation, where it depends upon the page rank of the incoming links.
Page Rank is independent of a website as whole. Each page of a website is calculated separately and represented by different page rank. The root directory does not necessarily to have the higher page rank than the sub-directories. The inner pages may gain a higher page rank than the home page.
Page Rank link juice is a widely discussed term in webmaster world. Page Rank link juice is the flow of authority form parent site to linked site. If you have a webpage of Page Rank 7 and you have one external link in the webpage. Then the link gets most out of the page rank. Whereas when the number of external links increases the link juice to each link reduces and divided. No-follow links do not contribute to page rank.
Multiple links for a single webpage is considered as one when calculating the pagerank. Only the Links from relevant and high quality sites do put an impact on pagerank. Also the internal links pass the pagerank juice.
The Pagerank of a website can decrease at any point of time if the websites linking to you experience a decrease in their page rank. Violation of Google guidelines also can cause a decreased page rank. Hidden text, cloaking, link exchanges, or anything against Google’s guidelines can trim down your page rank.