Simply put, affiliate programs, also called associate programs, are arrangements in which an online merchant Web site pays affiliate Web sites a commission to send them traffic. These affiliate Web sites post links to the merchant site and are paid according to a particular agreement. This agreement is usually based on the number of people the affiliate sends to the merchant's site, or the number of people they send who buy something or perform some other action. Some arrangements pay according to the number of people who visit the page containing their merchant site's banner advertisement. Basically, if a link on an affiliate site brings the merchant site traffic or money, the merchant site pays the affiliate site according to their agreement. Recruiting affiliates is an excellent way to sell products online, but it can also be a cheap and effective marketing strategy; it's a good way to get the word out about your site.

There are at least three parties in an affiliate program transaction:

In 1996, Jeff Bezos, CEO and founder of Amazon.com, popularized this idea as an Internet marketing strategy. Amazon.com attracts affiliates to post links to individual books for sale on Amazon.com, or for Amazon.com in general, by promising them a percentage of the profits if someone clicks on the link and then purchases books or other items. The affiliate helps make the sale, but Amazon.com does everything else: They take the order, collect the money and ship the book to the customer. With over 500,000 affiliate Web sites now participating, Amazon.com's program is a resounding success.

Over the past few years, affiliate programs have grown enormously in popularity, taking many interesting forms. For many Web sites that don't deal much in e-commerce (selling products or services online) themselves, functioning as an affiliate is a good way to participate in e-commerce.