The number of times an ad is shown to a target audience
An ad impression is counted each time an ad renders on a user’s screen within an app. Whether the ad is clicked is not taken into consideration. Impressions are a common metric to monitor ad performance because it provides a simple depiction of how many users are seeing ads within an advertising channel.
Ad impressions are often charged on a Cost per Mille (CPM) basis, whereby an advertiser is charged per thousand impressions.