Page rank was started by Google through the author, Larry Page, the co-founder of Google. Each web page in a website has a great value in Google. Ranking of a page is being scaled internally by Google to determine how important a web page is for a website. When Google determines that your web pages in your website have great importance to them, they will let you be listed to their index in Google Search Engine. They will also improve the ranking of your website.
Most page rank is based on the main page (landing page) of a website. We can see this when we use some tool that could check some page ranking for a website. But page rank that Google will give can entirely affect the whole web pages in your website.
There are many tools to be used in checking your page rank. One of the tools is called the page rank meter tools provided by seaquake, prchecker, googleranking, and many others. Actually most of these tools are free.
Note that Google updates a web page ranking only once in every 4-5 months. We have realized too that number of links is very important considering the quality of links. Using links or website that has a high ranking could help you improve your ranking. Example is linking your page to Facebook, Twitter, Linkin, blogs and many other known websites that has good page rank.
One factor in having a page rank is the use of proper keywords. This may include: Meta title tags, Meta description, Meta Keywords used, anchors text, and alt to the images used.