Affiliate marketing is an Internet-based marketing practice in which a business rewards one or more affiliates for each visitor or customer brought about by the affiliate's marketing efforts.

Affiliate marketing is also the name of the industry where a number of different types of companies and individuals are performing this form of Internet marketing, including affiliate networks, affiliate management companies, and in-house affiliate managers, specialized third party vendors, and various types of affiliates/publishers who promote the products and services of their partners.

Affiliate marketing overlaps with other Internet marketing methods to some degree, because affiliates often use regular advertising methods. Those methods include organic search engine optimization, paid search engine marketing, e-mail marketing, and in some sense display advertising. On the other hand, affiliates sometimes use less orthodox techniques, such as publishing reviews of products or services offered by a partner.

Affiliate marketing—using one website to drive traffic to another—is a form of online marketing, which is frequently overlooked by advertisers. While search engines, e-mail, and website syndication capture much of the attention of online retailers, affiliate marketing carries a much lower profile. Still, affiliates continue to play a significant role in e-retailers' marketing strategies.[