What Exactly is page Rank and Why page Rank is necessary for the website and how google calculated the page rank of the website means google can increase the page rank of the website is there any technique or algorithm used google for checking or increasing the page rank of the website.....
From Wikipedia: Its just a figure showing how important your site is... but, it doesn't mean that having high PR means good SERP.
in my own words : pagerank it's a "feature" from google scaling from 0 to 10. you can check your site pagerank with google toolbar (a green bar on toolbar). pr its calculated by backlinks, freshness, unique, and more things
PR means how many votes have you gathered online so as to make you trust worthy in the eyes of Google and how important are you in the eyes of Google. but there is no point in worrying about the PR of your website. continue with the work of your website and involve in legitimate marketing of your website. most importantly, provide something unique (easier said than done) you will achieve a high PR. but it is not necessary that PR always increases. in some situations it may even decrease and the degradation may be drastic. there is no one who can tell you everything about PR as it is one of the most confidential things of Google's business
I have recently added a blog post on my blog on PR and backlinks. Check out my blog link from my profile . I bet you'll understand everything about Pr and backlinks