When you turn on Find My iPhone, iCloud can help you get your missing device back. And if your device is ever lost or stolen, Activation Lock keeps your information safe and makes it hard for anyone to use or sell it.
When you sign in to iCloud.com or the Find My iPhone app, you can see your missing device on a map or play a sound. And you can use Lost Mode to lock, track, or remotely erase all of your personal information.
More Info:- Icloud Technical Support