Page Rank is Google’s measure of importance assigned to a web page on a scale of 1 to 10. You can check the Page Rank value of any page by downloading the Google Toolbar. Initially, most of these search engines relied on meta tags to classify the relevance of websites based on keywords in the tags. But, with time, search engine results became cluttered with sites that spammed their content with relevant keywords but displayed poor content for the visitor.
This threatened the very essence, credibility and importance of search engines. The founders of Google evolved a formula called Page Rank (named after one of Google�s founder Larry Page) where the algorithm would count the number of sites that link to a page and assign it an importance score on a scale of 1-10. More the number of sites that link to a page, higher its Page Rank.
One way inbound links are your links mentioned by the other websites, without your linking to them. On a website, each individual page acquires link popularity based on the pages that link to it. It�s difficult to obtain one-way link, but good, solid content on the website and ensure it.
It is an agreement between two websites to exchange links with each other, in order to boost ranking throughout any search engine.
Three way linking:
In this, the first website links to a second site, the second site links to a third, and then the third site links to the first one.