An affiliate marketing partnership between a publisher and affiliate can take many different forms, although only a few are genuinely popular. In all cases the affiliate receives a payment for getting a visitor to complete an action, whether that is purchasing a product, subscribing to an e-mail list or just visiting the page. Below are the four most common forms of affiliate marketing partnerships.

Cost Per Sale (CPS)

Cost per sale is the most common form of affiliate marketing. It simply means that for each sale the publisher make as a result of the affiliate, the affiliate get pays a commission. Usually this commission is a percentage of the profit made by the publisher for that particular sale.

This form is popular amongst publishers as it means that they only have to payout when they've made sales, and is popular amongst affiliates because the commissions can be generous. The two biggest networks of CPS offers are Clickbank and Commission Junction. Clickbank specialises in digital products, while Commission Junction has many more “brick-and-mortar” businesses looking for affiliates.

Cost Per Acquisition (CPA)

CPA is also sometimes referred to as cost per action. In a CPA affiliate partnership, the affiliate is paid money whenever a visitor completes a certain action. For example this action could be filling in a survey, joining an opt-in list or in some cases making a purchase.

CPA affiliate marketing has become more and more popular in recent years amongst affiliates because you can receive reasonably high payouts for some actions. Also, getting someone to join an e-mail list for example is often easier than getting someone to buy a product.

The money paid out for each action or acquisition varies for each publisher, and there are many CPA networks with thousands of CPA offers on the internet. Some popular networks are Azoogle, Commission Junction and CPA Empire.

Cost Pet Thousand Impressions (CPM)

Cost per thousand impressions is when a publisher pays an affiliate a certain amount of money for every thousand visitors sent, regardless of how many of these bought the product or completed an action. This kind of partnership is much less common today than CPA and CPS, mainly because publishers know that it is not the amount of visitors that they get to their sales page but the quality of the traffic that's important.

This kind of system also isn't popular amongst affiliates because the payouts are generally much less than CPA or CPS, reflecting the low value publishers give to this sort of partnership. However there are some companies that still offer CPM affiliate partnerships.

Cost Per Click (CPC)

This is similar to CPM, but instead the affiliate is paid on a per click basis. Again, this kind of partnership isn't favoured by publishers because the affiliate is paid regardless of whether any sales were made.

The vast majority of affiliate partnerships, some estimate up to 99% on the modern internet, take the form of CPS and CPA. This is because they give the greatest monetary benefits for both the affiliate and publisher.