Back in November 2016 Google released a stand alone app version of Android Auto that would only be used on a mobile phone. Previously the only way to use Android Auto would be to connect your phone to a compatible head unit.
While not exactly the same experience as using Android Auto with an in-car receiver, the more frugal users who did not want to spend the extra money on an Android Auto receiver were able to use the Android Auto functionality to add convenience and safety to their driving.
As things evolved with the Android 10 operating system Google integrated Android Auto, removing the need to have a stand alone app. For those users only using their phones and not an in-car Android Auto receiver they would now have to use the Android Auto for Phone Screens App.
Now fast forward to the release of Android 12 and Google has announced they will now be killing off the Android Auto for Phone Screens app. This is due to them wanting to migrate everyone over to Google Assistant driving mode. According to The Verge in a statement made by Google, “Starting with Android 12, Google Assistant driving mode will be the built-in mobile driving experience. We have no further details to share at this time.”