Affiliate Marketing is an Internet-based marketing strategy in which businesses reward affiliates (or partners) for each customer generated by an affiliate’s marketing efforts. Comscore reports that affiliate marketing accounts for 80% of all ad dollars spent online.

The Affiliate Marketing industry has four core players: Advertisers (also known informally as ‘Merchant’, 'Retailer' or 'Brand'), Publishers (also known as 'Affiliates'), Affiliate Networks, and Consumers. Advertisers are business with products and services to sell. Affiliate Network connect Advertisers to the traffic and marketing efforts provided by Affiliates. Sometimes, advertisers establish their own affiliate network and work directly with affiliates or use more than one affiliate network to promote their products and services. This market has also grown in complexity over the years, warranting a second tier of players, including Affiliate Management Agencies, Super-Affiliates and Specialized Third Parties vendors.

Affiliate marketing overlaps with other Internet marketing methods, because affiliates often use conventional online advertising methods. Those methods include contextual advertising, display advertising, e-mail marketing, organic search engine optimization, paid search engine marketing and social media marketing. Affiliates use these methods to generate customers for advertisers.