The biggest transformation is the design - Android Auto went for a darker theme that looks more like Apple CarPlay. It also added an app launcher (with all the applications in one place), new apps (Weather, Calendar, Reminders, News) and notification buttons.
If you Google “Android Auto BMW”, you’ll get tons of articles, forum threads and videos with tips & tricks on how to get it to work in your BMW. They might include installing an Android Auto head unit or ways to hack Android Auto, but we don't recommend either of those routes. The best solution would be to go for original software (if your BMW’s compatible with it) or choosing a trustworthy aftermarket retrofit like Android Auto MMI Prime.
In case there is no way to get Android Auto into your BMW, there are other ways to bring more features of the smartphone into your car with the help of BMW ConnectedDrive, Android Autolink, etc.