Standard
netvertising industry
jargon for
Cost Per Thousand.
If a certain banner advertising venture costs $5 CPM, then your ad will be displayed 1000 times for every $5 you drop on it.
Why it's CPM I may never know, it probably comes from the Roman Numeral M which means 1000. However, why this is the standard boggles my mind, I would think they'd use something more mainstream like Thousand or even Kilo (and yes I know that Kilobyte != 1000. shut up, you nerd.).