What is an ad impression?
An ad impression, also referred to as an ad view, occurs every time an ad is displayed and seen by the user within an app. Each time an ad is shown is counted as one impression. Impressions are measured in terms of cost per mille (CPM), which is a cost applier per 1000 impressions and indicates how much advertisers are charged and developers are paid for their inventory.
Why are ad impressions important?
Ad impressions allow advertisers to see the number of people viewing their ads and give a general idea about their apps’ performances, though they cannot be solely relied upon as they represent the base-level of data. Ad impressions also are important to calculate metrics such as click-through rate (CTR), impressions per daily active users (IMPDAU) or installs per mille (IPM.)