Cost Per Acquisition is a method of advertising

Advertising

Advertising is a form of communication used to persuade an audience to take some action with respect to products, ideas, or services. Most commonly, the desired result is to drive consumer behavior with respect to a commercial offering, although political and ideological advertising is also common...

whereby the advertiser only pays when
an advert delivers an acquisition. Moreover, CPA is very effective for an advertiser to pay because they only pay when the advertising has met its purpose. The publisher relies on the conversion rate of the advertiser’s web site, something which the publisher cannot control. CPA model is not usually used for banner advertising and is usually linked with affiliate marketing.