Some apps need to access notifications from other apps to work properly. For example, a smart driving companion app needs to access notifications from other apps in order to read them aloud when you're driving.
Be sure that apps with access to your notifications have legitimate reasons, because with this access they can:
Tap an app to see which notifications it can access:
Choose one:

If you restrict an app's access to notifications and then find the app isn't working properly, you can restore access.

If you've set a pattern, PIN or password, you can control which type of notifications show on your lock screen and prevent them from revealing private information.
To adjust notifications for all apps:
To hide sensitive content on your lock screen, turn Sensitive notifications off 
You’ll get lock screen notifications for an incoming email or chat, but they won’t include message details.
For finer control, leave this on 
To hide sensitive content from specific apps:

Types of notifications the app sends appear here. For each enabled notification that you want to hide: