Samsung
Turn Background Data Usage On or Off auf Samsung
Background data lets an app exchange information with its servers even when you are not looking at the screen. This is how messaging apps deliver notifications instantly and how mail or cloud apps stay up to date without you opening them first.
On Samsung phones, this behavior is controlled per app in the system settings. Each app has its own toggle, so you can allow background data for apps you check often and block it for apps that only matter when opened, like games or rarely used tools.
To change it, go to Settings ➔ Apps ➔ Choose an App ➔ Mobile data ➔ Allow background data usage. Turn the toggle off to block that app from using mobile data in the background, or turn it on again to restore normal syncing.
Disabling background data reduces mobile data consumption and can extend battery life, since the app stops waking up on its own. The trade-off is delayed notifications and content that only updates when you manually open the app.
If your main goal is saving battery rather than data, check the app's battery settings instead, since aggressive background restrictions there can achieve a similar effect without touching data permissions app by app.