In iOS, it features the Background App Refresh, allowing background applications to refresh continuously to update new information, such as Facebook, which will refresh news feeds and notifications regularly. This will help us every time we open the app without refreshing to refresh, but there are disadvantages that will consume DATA 3G / 4G when the device is not connected to WiFi, as well as consuming more battery power.
The refresh app background can be turned on / off easily in Settings -> General. However, even if we are turned off, in each app, they are still granted permission to refresh their own background, so if you want to turn it off, you should turn on each specific app and turn off Background app. Like yesterday, after I turned off the background app refresh in each app, the battery life of the device increased by 10-15%.
I wish you happy iOS!