Cost Per Mille (CPM) is a metric used in affiliate marketing to measure the cost of an advertisement that reaches 1,000 viewers or impressions. It is typically used to measure the cost of online advertising campaigns, as it is easily calculated and can be used to compare the cost of different campaigns. CPM is calculated by taking the cost of the advertisement and dividing it by the number of impressions it received. For example, if an advertisement cost $500 and received 50,000 impressions, then the CPM for that ad would be $10. By using CPM, advertisers can gauge the effectiveness of their campaigns and compare the performance of different ads.For example, if an advertiser has two ads that are running on the same platform and one has a CPM of $10 and the other has a CPM of $20, then the advertiser can easily see that the first ad is performing better and is more cost effective. By using CPM, advertisers can make sure that they are getting the most out of their advertising budget and are able to optimize their campaigns to get the best results.