Affiliate marketing involves merchants paying publishers to advertise their products on other websites. Merchants only pay affiliates for sales or leads generated from the ads. This allows merchants to expand their reach while managing marketing costs. Key players are affiliates who host ads on their sites, merchants who are advertised, and affiliate networks that facilitate tracking and payments between affiliates and merchants. Affiliates are typically blogs, forums or other content sites that earn commissions from sales made through links on their pages.