Cost per mille (CPM) is the cost an advertiser pays per one thousand impressions. Impressions here mean the number of views or other actions taken by the recepient. CPM is the most common metric in programmatic media buying and is often used to measure digital advertising campaign performance.
For example, if an ad publisher charges $3 CPM, the advertiser needs to pay three dollars per one thousand impressions.
The word mille is Latin for “thousand.”