Article marketing is the practice of posting keyword-focused articles on article sites that then syndicate your content. The reason this is an important website promotion technique is because some of these article syndication sites have a significant readership following.
Most article syndication sites allow you to post your content for free. Once published, your content becomes available for all to see - and potentially reuse. When done properly, articles you post on syndicated article sites can then become "link bait" for other sites. For example, let's say you own a home business that sells closet organizers. If you or your web content writer write an article about organizing your office, others who may want to post a blog entry about organizing your office may link to your article, getting increased exposure for your writing and your subject matter, especially if the article site gets a great deal more traffic than your own website, which is fairly likely.