What is Android SystemUI used for?

With system UI, apps can adhere to the Home screen, notifications, and global device navigation experience as envisaged by Google. The System UI Tuner was first spotted when the Android Marshmallow preview was launched back in 2015. It existed as a customization menu in the Settings app.

What happens if system UI has stopped?

System UI error may be caused by a Google App update. So uninstalling the update may fix the problem, as the Android platform depends on its service to run other applications.