App data usage
The Data usage option inside the information for an app in the Apps settings shows the amount of data that has been used by the app within the last period, and gives options for restricting the app's data use while in the background, or exempting it from the Data saver feature.
Disable this switch to prevent the app using data when the app is not in use (such as when the device is asleep or you are using a different app).
For some apps, this may interfere with the ability for the app to completely function. Some apps need to be able to use data in the background for certain features.
This switch is enabled by default.
Unrestricted data usage
Enable this switch to allow the exempt this app from the Data saver feature, allowing it to use data as it normally would even when Data saver is switched on.