Minimum CPM, or cost-per-mille, is a pricing model used in the online advertising industry to refer to the minimum amount that an advertiser is willing to pay for 1,000 ad impressions. Minimum CPM is often used in the context of programmatic advertising, where ads are bought and sold through automated auctions or marketplaces. In a minimum CPM auction, advertisers can set a minimum CPM bid, which is the minimum amount that they are willing to pay for each 1,000 ad impressions. If the auction determines that the ad will be delivered to at least 1,000 users, and that the ad's value is equal to or greater than the minimum CPM bid, then the ad will be served, and the advertiser will be charged the minimum CPM bid. Minimum CPM can be a useful pricing model for advertisers, as it can help to ensure that they are paying a fair price for their ad impressions, and that they are not overspending on their advertising budget.