Once Find My is enabled on an iPad, iPhone, Mac, or Apple Watch, the device cannot be unlocked without the iCloud password ... at the top (where it says Apple ID, iCloud, iTunes & App Store).

Apple's iOS software has an ability to Find your iPhone/iPad/Mac computer if you lose it ... anybody who finds your device is unable to factory reset your device and use it again without your iTunes ...

Turn on Find My from Apple Account settings, and enable Location Services from Privacy & Security This article explains how to set up Find My (or its predecessor Find ...