Ads for mobile apps in Yandex.Direct are a special ad format designed specifically to promote mobile apps: attracting new users, increasing installs and returning previous users who are now inactive. From the ad, user are redirected straight to the app's page in the relevant app store, where they can download it in as few steps as possible.
UPD from 08.09.20: We added a checklist that takes all recent changes to Ads for mobile apps into account.