Cost per thousand and Cost per mile also known as CPM is a metric used to depict the price of 1,000 impressions on a website. For instance, if a publisher charges a $5.00 CPM this means the advertiser must pay $5.00 each time 1,000 impressions are made.
Some disadvantages to the CPM metric are overcounting due to duplicate viewing, ads that fail to load/glitch, or fraud, whereas advantages are that it can help advertisers better allocate their budgets, understand where to place ads for maximum visibility, and track campaign/channel performance.
Use the CPM metric in your business to better determine advertising allocations within your budget and maximize on impressions.