Lost Mode is a feature available on devices like the iPhone and iPad that helps users locate their lost or stolen devices. When activated, it locks the device and displays a custom message on the screen, such as a contact number, to assist anyone who finds it in returning it to the owner. In addition to locking the device, Lost Mode also tracks its location using GPS technology. Users can view the device's last known location on the Find My app, making it easier to recover the device. This feature enhances security and increases the chances of retrieving lost items.