Also known as CPA. Here’s how it differs from PPC advertising. When running a pay-per-click campaign, an advertiser has to pay each time a visitor clicks on his ad and is brought to his landing page. There is no guarantee that the user will go on to purchase his product/service. CPA (cost per action) marketing on the other hand involves the visitors taking a desired action and not merely clicking on the ad (eg: filling out a form, ordering a trial version of a software product) and the advertiser is only charged after an action has been successfully completed.