What's the difference between display ad models CPA, CPC and CPM?
CPA stands for cost per acquisition or action, it means you pay for ads based on a specified goal achieved such as a sale or lead form completion.
CPC stands for cost per click which means you pay for your ad based on the number of clicks it gets.
CPM stands for cost per mille (cost per 1000 impressions) which means you pay for your ads based on how many times they are seen by your audiences.