Cost per thousand (CPM), also called cost per mille, is a marketing term used to denote the price of 1,000 advertisement impressions on one web page. If a website publisher charges $2.00 CPM, that means an advertiser must pay $2.00 for every 1,000 impressions of its ad. The "M" in CPM represents the word "mille," which is Latin for "thousands."
Cost per thousand (CPM) is the most common method for pricing web ads in digital marketing. The method relies on impressions, which is a metric that counts the number of digital views or engagements for a particular advertisement. Impressions are also known as "ad views." Advertisers pay website owners a set fee for every thousand impressions of an ad. While an impression measures how many times an ad was displayed on a site, it does not measure whether an ad was clicked on.
The click-through rate (CTR) measures whether an ad was clicked on, representing the percentage of people who saw the ad and clicked on it. Advertisers frequently measure the success of a CPM campaign by its CTR, For example, an advertisement that receives two clicks for every 100 impressions has a 2% CTR. You cannot measure an advertisement's success by CTR alone because an ad that a reader views but does not click may still have an impact.