Samsung Reactivation Lock
Samsung Reactivation Lock is a function designed to protect your device if it is lost or stolen. The Reactivation Lock will keep the device from being used unless the appropriate Samsung Account Credentials are entered after a Factory Data Reset.
It's important to remove your Samsung Account from a Samsung phone or tablet that you're giving to someone else to use. Not only will it retain your information as long as you're logged in, the Samsung Account will lock anyone out without your Samsung Account email address and password.
To check whether your device has Reactivation Lock enabled:
You'll only be able to switch Reactivation Lock on when there is an active Samsung Account added to the device.