What is the use of Google Settings app? I'm using low config Android mobile, Google Settings app occupy my phone memory so I wonder to know what are the uses of behind this app and once I delete how come get back this app.
This app is actually part of the Google Play services app. Google automatically updates Google Play services on all supported devices via Google Play Store to ensure API consistency across devices and versions, and to deliver fixes and new features in a timely fashion.

It is installed on any Android device running Android 2.2 or higher and is updated every 6 weeks and the updates are pushed silently to all supported devices meaning if you uninstall it then it will be re-installed automatically.

It also allows Google to patch some vulnerabilities in Android without requiring a full O/S update or involving manufacturers/carriers.