For more information about Activation Lock as an iOS feature, read the Apple Support article Find My iPhone Activation Lock.
When Activation Lock is enabled, an end user’s Apple ID and password are required to unlock a device even if the device is wiped or factory reset, including through DFU mode. This feature makes it difficult for unauthorized persons to use a lost or stolen device. Activation Lock is a security feature for devices running iOS 7 and higher that uses Apple’s Find My iPhone functionality.
