CPM is one of the most commonly used metrics. It is an abbreviation for “cost-per-mille,” where “mille” is a Latin word which means “thousand.” As such, this metric indicates that the cost of CPM advertising is calculated based on measured impressions. For every thousand impressions, advertisers pay Google a certain amount of money.
CPM measures the cost of a digital advertisement per 1000 impressions. When the ad is shown on YouTube or Google Display Network (GDN), it is counted as an impression.