Affiliate marketing began just four years after the world wide web was launched, originally popularized by well known companies such as CDNOW or Amazon.com. Google's Adsense is also a very well known type of affiliated marketing, but is not really considered as true affiliate marketing as the adverts usually centers around the theme of the website they are displayed (known more as contextual advertising.) Google does not also directly sell a specific product, but generates money in other ways.
Affiliate marketing is highly cost-effective, and in effect costs both the advertiser and the affiliate nothing, while having the potential of bringing in a very large form of income for both parties. While pay per click (or cost-per-click) mentioned above can present a risk to the advertiser, the cost-per-sale (CPS) system has very little or no risk at all for both parties, and is therefore preferred.