Display Ads, also referred to as Banner Ads, are rectangular graphic displays on the side edges of an application or website.
Ad servers usually deliver banner ads to a certain application or website where these are then displayed. Now, the user can click on this banner and is then taken to the App Store or a corresponding landing page. Since the format of display ads is largely accepted, advertisers can easily place their advertisements in apps or on websites. Furthermore, publishers can accept ads from most advertisers.
Display ads are usually paid through cost per impression, cost per click, or cost per action. Mostly, their aim is to promote a brand or to activate or reactivate users.
They are image-based rather that text-based and are the most popular form of online advertising. They have been the most popular form of mobile advertising for the last years but seem to drop in popularity as native and video ads become more popular.