The term Ad Impression describes the amount of times an advertisement is displayed within an app or website.
Ad Impressions are highly important for online marketers because they measure the volume of an online marketing campaign. Ad Impressions must not be confounded with Ad Views, which measure the amount of times an advertisement is being looked at. Since not every advertisement that is displayed on a website or in an app is also being looked at by a user, it is important to differentiate between those units. Nevertheless it is not always possible to measure whether an ad has been viewed by the user. Therefore the number of Ad Impressions is equated with the number of Ad Views by the publishers.
The number of Ad Impressions will usually be protocolled by the Ad Server. Protocolling the number of Ad Impressions is important for several reasons.
For one in order to deduct the ad budget correctly. A lot of ad campaigns are settled by the pricing model CPM – Cost per Mille, for which the advertiser pays for every 1000 impressions his ad got.
Another reason why it is important to measure Ad Impressions results from the way the ad budget gets deducted. Since advertisers pay on a CPM basis, it is important to also measure results like clicks, leads, sales and orders. That way advertisers are able to calculate the effectiveness of ad spend when comparing those numbers to their ad spend for every 1000 impressions.