An automated marketing program where a Web advertiser or merchant recruits webmasters to place the merchant's banner ads or buttons on their own Web site. Webmasters will receive a referral fee or commission from sales when the customer has clicked the affiliate link to get to the merchant's Web site Web site to perform the desired action, usually make a purchase or fill out a contact form. The most common types of affiliate programs include pay-per-click, pay-per-lead, and pay-per-sale.
See "How Affiliate Marketing Works" in the "Did You Know..." section of Webopedia.
Also see Refer-It.com, a directory of referral & affiliate programs for e-commerce, featuring information on over 6,500 affiliate programs.