The Privacy option controls whether the content of a notification pops up on the screen or not.
- Press START means that you need to press the start button to see the content. So if a message arrives, the name of the app pops up on the screen but the content of the message isn't visible until you press the start button.
- Gesture is similar, only instead of needing to press the button you can turn your wrist to look at the watch for it to show the content.
- Off means that the content of the message is shown when the notification pops up.
It's described as a privacy feature because it hides notification content until you interact with the watch, meaning your messages don't become immediately visible to anyone who can see your wrist.
