Factory Reset Protection (FRP) is a security feature that prevents unauthorized users from using a device that has been hard factory reset. This feature is applicable in a situation where a malicious user is in possession of a lost or stolen device and has performed a hard reset from the bootloader. If FRP is enabled, then the account credentials of only an authorized user can be specified on the device, without which the device is rendered unusable.
NOTE:This feature is not applicable for Android 6 (Marshmallow) devices.