Pagerank is a concept used in search engine optimization to describe a measure of how important your website appears to be. Although it is not the only deciding factor that search engines use when deciding what pages to show in their results, it is still very much an important part of how your site will perform in search engine rankings. A Google pagerank will range from 1 to 9 - with a pagerank of 9 being very much the acme of success. Although the way that search engines actually calculate pagerank is kept secret from webmasters the general methods have been made available. Generally speaking, your pagerank is greatly improved by the number of other pages that link to yours. These are called "backlinks".
The more reputable the website linking to you, the more PageRank will be conferred to your site. In other words, having good websites link to you gives your site a better reputation just by association.
So it seems that as search engine optimization (SEO) professionals we must devote time and effort to attracting high quality backlinks. This is not as easy as it sounds, however. An old practice used to involve swapping links - this sort of reciprocal linking arrangement was seen as a quick alternative. It is very important to note that Search Engine companies work very hard to try and identify artificial means to game their systems. The whole point around counting the number of sites linking to you is to try and identify sites that have worthwhile content on them. Reciprocal and paid linking suggests that your site content is not good enough to attract attention without "bribing" other sites. As such these practices are generally frowned upon, though still very much in practice.
Submitting your site to Internet directories is one way to get links. A particularly important directory is DMOZ, which Google pays careful attention to because it is human edited and not automated. This implies that the links can be expected to have a higher quality. A significant drawback with using DMOZ is that it is often slow, or even impossible, to get your site listed because of the backlog of requests. In some cases you could expect to wait several months before your request is reviewed.
Writing articles that link to your website is another way to generate backlinks. There are many websites that specialize in offering authors an opportunity to write an article that links back to their own website. A South African example could be ePress. Other alternatives include posting on forums or commenting on blogs. Social bookmarking sites also offer a way to link to your website - either through your user profile or by openly sharing links with other users.
Building an effective backlinking campaign is an important part of developing an SEO strategy. The modern Web allows for more creative methods of doing so - ways that involve socializing and discovering new sites. It is still very much an art form and takes practice to perfect.