Impression

This refers to the numerous times an ad is displayed. In pop-ads, one “pop” of a webpageA single page that is a part of a much larger site. It can be a landing page, a blog page, a homepage, or any other part of a website. is counted as an impression. In display and text-link ads, an impression is counted whether or not the ad is in the viewable range. A viewable impression, on the other hand, is counted when at least 50% of the ad appears in the viewable range for at least a second.