Backup & reset settings
The Backup & reset settings menu provides settings related to backing up the data on your device. This allows certain settings such as Wi-Fi passwords, and certain application data to be restored after resetting the device.
Some devices will have additional options here, such as options specific to your device manufacturer.
Back up my data
This setting controls whether the backup service should run on this device.
Google's backup and restore functionality should be considered a convenience only. You should not use it as your sole backup, and you should always back up videos and photos you have taken.
This setting allows you to choose which Google account your backups should be associated with.
Not all backed-up data can be restored to any device: when switching to a new phone, most app settings will not be transferred, whereas other settings such as Wi-Fi settings can usually be carried across.
Enable the backup service to restore settings when reinstalling apps that you have previous backups for.