Affiliate Marketing is a popular method of promoting web businesses in which an affiliate is rewarded for every visitor, subscriber and/or customer provided through his efforts. It is a modern variation of the practice of paying finder's-fees for the introduction of new clients to a business. Compensation may be made based on a certain value for each visit (Pay-per-click), registrant (Pay-per-lead), or a commission for each customer or sale (Pay-per-Sale).

The most attractive aspect of affiliate marketing, from the merchant's viewpoint, is that no payment is due to an affiliate until results are realized.

Some e-commerce sites, such as Amazon.com run their own affiliate programs while other e-commerce vendors use third party services provided by intermediaries like Commission Junction, ClickBank and/or LinkShare to track traffic or sales that are referred from affiliates. Some businesses owe much of their growth and success to this marketing technique.

Merchants who are considering adding an affiliate strategy to their online sales channel should research the different technological solutions available to them. Some types of affiliate management solutions include: standalone software, hosted services, shopping carts with affiliate features, and third party affiliate networks.

In its early days many internet users held negative opinions of affiliate marketing due to the tendency of affiliates to use spam to promote the programs in which they were enrolled. As affiliate marketing has matured many affiliate merchants have refined their terms and conditions to prohibit affiliates from spamming.

Currently there is much debate around the affiliate practice of Spamdexing and many affiliates have converted from sending email spam to creating large volumes of autogenerated webpages each devoted to different niche keywords as a way of SEOing their sites with the search engines. This is sometimes referred to as spamming the search engine results.