Referring domain is the domain from which you receive backlinks. Backlink is essentially a website page that links back to your publisher website. Affiliates are constantly looking to improve backlinks to their website to increase search engine visibility. However, referring domain figure is much more important than backlinks. Receiving multiple backlinks from the same domain is not going to help publishers to improve their page rankings. Search engines continue to penalize websites that use shady tactics to increase backlinks. To strengthen page ranks of a publisher website, you need to maintain a high ratio of referring domain to backlinks.