By default, when you open the iTunes App Store, videos automatically play on apps or other news. The background is what's called video content.
The default setting for this is "On" and thus set for the automatic playback of videos. However, this can bother you, because data is consumed unnecessarily when connecting to a mobile data network.
Therefore, follow the instructions below to switch off automatic playback within the App Store.
Turning off video auto play for iTunes and App Store - How to do it
1. Open the settings
2. Select the entry "iTunes & App Store
3. Set the slider to inactive for "Video Auto play
Alternatively, you can set the App Store to play videos automatically only when you're connected to a W-Lan network.