Activation Lock in Find My iPhone
Find My iPhone includes a feature called Activation Lock that is turned on automatically when you set up Find My iPhone. Activation Lock helps prevent anyone else from using your iPhone, iPad, iPod touch, Mac or Apple Watch if it is ever lost or stolen.
Note: Activation Lock is available for Mac models with a T2 Security chip that have macOS Catalina 10.15 installed.
With Activation Lock, your Apple ID and password are required before anyone can do the following:
Turn off Find My iPhone on your device
Sign out of iCloud on your device
Erase and reactivate your device
If you lose your device and remotely erase it, Activation Lock remains on. Your Apple ID and password are required to reactivate the device. If you reset your device and erase all content and settings, Activation Lock is turned off. See the Apple Support article Activation Lock for iPhone, iPad, iPod touch, and Apple Watch.
Important: Make sure that you remember your Apple ID and password, and that your password is unique and secure — someone else should not be able to guess it. See the Apple Support article Security and your Apple ID.