Cost Per Impression
Cost per impression (CPI) or CPM (Cost per mille) are phrases used in online advertising and refer to volumes of web traffic in relation to nominal exposure gained for the advertiser via the given online platform. CPI involve online marketing campaigns in which advertisers pay for every time that their advert is displayed to a user, though can also denote ads via Email advertising.
An impression is simply the rendering of a web page that contains the advertisers advert. A given web page often contains more than one advert and in such cases a single pageview would result result in one impression for each advert displayed to that user.
In order to count impressions accurately and circumvent fraud, an online advertisement server will often exclude actions such as refreshes or other actions from counting as impressions. When online advertisement prices are described as CPM/CPI, this how much every thousand impressions rendered of the given advertisement online will cost the advertiser.