Ghost mode gives you the option of either blurring or freezing your real-time location. No notifications are sent to you've friends upon being ghosted.
We don't tell your friends when you enable frozen mode for them. It will look like you have no signal or that your phone is off. Your map pin will remain on the last live real-time location acquired by Zenly before freezing your location.
However, friends, who you've chosen to blur, will see the blurred blue icon (image below) at the bottom-right of your map pin, indicating that you are somewhere in the general vicinity.
Learn more about Ghost Mode.