The cost per 1000 impressions, also known as CPM, is a metric that allows advertisers to understand the amount they need to pay for 1,000 ad views on their page. For instance, if the CPM is $5, it means that advertisers have to allocate $5 for every 1,000 times the ad is viewed. This metric provides an estimate of the cost involved in reaching a specific audience and is widely used in digital advertising to measure campaign effectiveness and budget allocation.