PageRank (PR) is Google’s numerical system of ranking the relative importance of all web pages within their database. In Google’s own words, PageRank calculates the “uniquely democratic nature of the web by using its vast link structure as an indicator of an individual page’s value.” In simpler terms, their system of ranking is based on incoming and outgoing links. It is, in essence, a sort of popularity contest whereby a link to a web page is basically considered as a vote for the importance of that page. The more inbound links that a web page has, the more popular, and thus the more important, that page is thought to be.
A PageRank is given to each individual page within a website, thus it is not the site itself that has a PR but each page within that site. For instance, if you have a website for your plastic surgery practice, you homepage may have a different PR than a page on breast augmentation, and a page on rhinoplasty may have a PR that is different from both of them. PageRank can range in numbers from 0 to 10, with 0 being the lowest and 10 being the highest. PageRank is expressed as a PR0 to a PR10. PR0s rarely occur under normal conditions, which is fortunate because a PR0 makes it very difficult for a page to rank well in search engine results. A PR0 typically results from either having a page that has been in existence for three months or longer and has received no inbound links or from being penalized by Google.
Moving up in PageRank is not done through a series of equal steps. Instead, PR is similar to the Richter scale in that it is exponential in its calculation so that each level becomes progressively harder to reach. It is more difficult to move from a PR2 to a PR3 than from a PR0 to a PR1, and more difficult still to move for a PR4 to a PR5 and so on. Further, the incoming links, or votes if you will, are not all equal. Some votes are more important than others. Links from pages with a higher PR are given more importance and more value than links from pages with a lower PR. Though every inbound link will add some PR, it may take significantly more PR3 incoming links to boost a page’s PR than it would for PR6 incoming links. As such, the more incoming links from higher PR pages, the better. Yet another aspect that factors into the equation is the amount of outgoing links from the sending page, or the amount of overall ‘votes’ that they give out. A page will get less PR if the incoming link is just one of many by a given sending page or ‘voter’. As such, it’s theoretically possible to get more PR from an incoming link from a PR3 page if you’re the only recipient as opposed to an incoming link from a PR7 page that has sent out 100 links.
As confusing as it can be, the bottom line is to add as many incoming links as possible since all links add PR to some degree. Further, once a good PR has been achieved, incoming links must still be added in order to maintain that PR. As a page’s PR grows, that page will move higher in the search results for targeted keywords.