Link building Companies are know ae SEO companies in general. The biggest difference is that they deal with link building all day long. If you have a new web site you will benefit by hiring one of these companies to gat a few good links to your new website right away. The search engines use your link data to help rank your site. In other words if you have good relevant back links coming to your site you have a great chance of getting a good search term ranking and good page rank for you site. Today many of these site and companies are coming out of India.