Cost Per Action
Cost Per Action is an online advertising pricing model, where the advertiser pays for each specified action (a purchase, a form submission, and so on) linked to the advertisement. The CPA can be determined by different factors, depending where the online advertising inventory is being purchased.
Most CPA offers by advertisers are about acquiring something (typically new customers by making sales). In CPA campaigns, the advertiser typically pays for a completed sale involving a credit card transaction. Cost per action is a means of controlling advertising spend. CPA also offers an opportunity to control ROI.