CPA stands for Cost per Action or Acquisition. It defines the cost associated with each lead or sale created by the click on the advertisement, regardless of the number of impressions or clicks the ad gets. This method allows the advertiser to closely manage his ROI and advertisement costs, but tend to be more expensive. Generally, it is a metric system which calculates how much clicks on your ad is needed in order to get a conversion. It tends to be more expensive because not everyone who clicks on your ad will go on to finish the action you wished for. So if you enhance your conversion rate it will lower your cost per action. There is a way to control your advertising spending and its called Cost Per Action bidding. So, instead of paying Google every time someone just clicks on your ad, without doing anything, you can choose to pay for your ad only when a conversion has been made. You can set up what that conversion will be, whether a sale, a lead, a download, anything you define. Cost Per Action advertising can help you avoid paying for search terms that are not helping you with the business.