Cost per action (CPA) is a type of ad where you get charged based on the action of the user on the ad. The action could be a sale or a lead. CPA is advantageous for advertisers because you only pay when there is lead or sale. It prevent you from paying for clicks that don't convert and using up your capital quickly. You can lose money if your campaign has a low leads to sales ratio. if you want to use CPA advertising, you must come up with a plan on converting the leads to sales.