The Always on Display feature is used to make sure that the display on your Apple Watch always turns on when you turn your wrist to the position where you are watching the time.
Always On has settings that let you turn the feature off, which can increase battery life. You can also choose the information that you want to appear on the screen when your wrist is down.

How to turn the Always On feature on or off:
1. Open the Settings app on your Apple Watch. To do this, press the Digital Crown to see the Home screen, then tap the Settings button;
2. Tap Display & Brightness;
3. Scroll down, then tap Always On;
4. Tap Always On to turn on or turn off the feature.

How to manage the information that appears when your wrist is down:
1. Open the Settings app on your Apple Watch;
2. Tap Display & Brightness;
3. Scroll down, then tap Always On;
4. Tap Show Complications, Show Notifications, or Show Apps. The apps that can show that type of information appear on the next screen;
5. Turn off the apps that you don't want to show information on the screen when your wrist is down. You can turn off the category of information entirely by tapping the button at the top of the screen.