PageRank (PR) is a method used by Google to determine the quality of links pointing at a website, and therefore the perceived importance of such a site online. PR is scored from 0 to 10, with only a very few websites having a PR of 10. Even Facebook and Google have a PR of ‘only’ 9, which should give you an idea of what level your site needs to be at to achieve a 10.
PR works by transferring ‘link juice’ from one page to another. For example, if you earn a backlink through an article on a high quality website, you’ll boost your own PR and authority as a result. If yours is the only link in the article, you’ll receive the maximum possible benefit, while if there are numerous links, the ‘link juice’ is spread evenly among them.
You can also build your PR by using internal linking. Although you need to be careful of doing too much ‘exact match’ anchor text linking, you can still grow the relevance of your site in Google’s eyes by using this technique sparingly.
PR shouldn’t be the only thing you think about when link building or pursuing your SEO goals, and you should also keep in mind that Google will view a long article with only one link as unnatural and low quality.