CPM, or cost per thousand impressions, is a pricing model used in online advertising, including Google Ads. In the CPM model, advertisers pay a fixed amount for every 1,000 impressions (views) of their ad.

For example, if an ad has a CPM of $2.00 and it is displayed 1,000 times, the cost to the advertiser would be $2.00. If the ad is displayed 2,000 times, the cost would be $4.00, and so on.

CPM is often used as a benchmark for measuring the effectiveness of an ad campaign, as it provides a way to compare the cost of an ad campaign to the number of impressions it generates. Advertisers may choose to use the CPM pricing model if they are primarily interested in increasing brand awareness and reach, rather than driving specific actions, such as clicks or conversions.

In Google Ads, advertisers can choose to bid on CPM or use a different pricing model, such as cost per click (CPC) or cost per action (CPA). The choice of pricing model will depend on the specific goals and objectives of the ad campaign.