Both affiliate marketing and CPA marketing involve the same visitor-affiliate-business relationship. However, in CPA marketing, you don't necessarily have to make a sale to earn a commission. The users only have to take a specific action, whatever it may be. Secondly, in CPA marketing, the commission is mostly a flat rate or a fixed price. In other affiliate marketing models, you generally get a percentage of the conversions you drive. For example, 10% of the purchase the customer made.