Find my iPhone, sometimes also called Find my iPad or Find my Mac when referring to the same app running on those devices, is a free service offered by Apple as part of iCloud. With it, you can track your iPhone, iPad, or Mac if it ever gets lost or stolen, lock it to make sure no one else can get into it, play an alert sound to help you find it, and even wipe it remotely if you're sure you won't be getting it back. It also enabled Activation Lock, which stops anyone without your password for using your device if it's ever stolen.
To use Find my iPhone all you need is the free app, iCloud.com, and this guide!
Before you can start using Find My iPhone, you'll need to set up the service. As long as you're signed into your iCloud account on all your devices, it's as simple as flipping a switch. After that, you can start tracking any devices linked to your account.
Family Sharing is available on devices running iOS 8 and up. Not only can you share purchases with other family members in your household, you can also keep track of each other with Find My iPhone. It works pretty much the same way as tracking your own devices does. As long as the person you'd like to track is a member of your Family Sharing group, you can always track them via Find My iPhone.
How to remove an iPhone, iPad, or Mac from Find My iPhone and iCloud
If you're upgrading to a new device and are either getting rid of or passing down your old one to someone else, you'll want to make sure that you disable Find My iPhone and remove your iCloud account. This does two things: it allows the new owner to link the device to their own iCloud account without any trouble, and it ensures that they don't have access to any of your information in your iCloud account.
How to turn off Find My iPhone remotely and bypass Activation Lock
If you've already gotten rid of an iPhone, iPad, iPod touch, or Mac and forgot to turn off Find My iPhone, there is a way you can remove it from your account remotely. This is the guide you want if you sold your device and the new owner tried restoring and can't get past Activation Lock. Just keep in mind that it doesn't work unless you know the iCloud password for whatever account the device is linked to.
What happens if you find an iPhone, iPad, or Mac left behind at a coffee shop, park, classroom, or bar? Find my iPhone is great not only for helping you keep track of your own devices, but helping you return a lost device to someone else.