I recently read that Google calls "Android Automotive OS" now "Google built-in". On some different articles i read that it's still called AAOS and Google built-in is only used for the Google Services(Play Service, Maps etc.) that you can use if you decide to use AAOS as a system.
At first I thought AAOS and Google built-in is the same but now im unsure.
"Google built-in" is the marketing name for Google Automotive Services (GAS), which is a licensed product sold to car OEMs consisting of Google Maps, Google Assistant, the Google Play Store, etc.
GAS runs on top of Android Automotive OS (AAOS), which is an open source operating system. If you're familiar with the phone/tablet world, GAS is like Google Mobile Services (GMS) while AAOS is like "regular" Android.
See this Wikipedia article for more details, including a list of vehicles which run AAOS with/without GAS.