What does CPM mean?

Cost Per Mille, and more popularly Cost Per Thousand (Mille = Thousand), or CPM, is an advertising cost structure based on the number of impressions served, but not necessarily seen. Traditional media may base CPM on distribution numbers or households and for digital advertising, CPM is based on the number of impressions loaded, and vCPM (Viewable CPM) is a pricing structure based on the majority of the ad being seen. Social media and programmatic display advertising platforms most often use CPM as a basis for cost.