CPA, or cost per action, is a pricing model used in online advertising, including Google Ads. In the CPA model, advertisers pay a fixed amount for each specific action that is attributed to their ad campaign. The specific action could be a purchase, a form submission, or some other desired outcome.

For example, if an ad campaign has a CPA of $5.00 and it results in 100 purchases, the cost to the advertiser would be $500.00 (100 purchases x $5.00 CPA). If the ad campaign results in 200 form submissions, the cost would be $1,000.00, and so on.

CPA is often used as a measure of the effectiveness of an ad campaign, as it provides a way to compare the cost of the campaign to the number of specific actions it generates. Advertisers may choose to use the CPA pricing model if their primary goal is to drive specific actions, such as purchases or form submissions.

In Google Ads, advertisers can choose to bid on CPA or use a different pricing model, such as cost per click (CPC) or cost per thousand impressions (CPM). The choice of pricing model will depend on the specific goals and objectives of the ad campaign.