CPA is a common term in terms of online advertising and is the abbreviation for cost per action. CPA is used in affiliate marketing programs wherein the publisher and advertiser agree upon this model of cost payment. Affiliate marketing is part of indirect marketing and is very effective in promoting online business. In this, the advertiser advertises his site on another website and draws traffic from there. The publisher earns revenue for it. The income that he earns is set on different payment methods. The cost per action payment method is based on the visitor’s action. When the traffic is diverted to the advertiser’s website then he gets to earn when he performs a particular action. This action can be signing up for newsletter, playing contest or any other such things. So every time the visitor performs this action , the publisher would earn for it. Thus the term, cost per action. This kind of affiliate marketing programs is considered to be more effective in bringing in quality and is therefore preferred by the advertisers as it makes their ad campaign more cost effective. The publishers also earn better revenues in this payment model and use it for sending quality traffic to another website.