Android Auto is Google's solution for bringing the power of your smartphone to the relatively dumb nature of vehicle infotainment. Basically you're using your phone to broadcast a new user interface onto your car's touchscreen, thus bringing the full power of Android 5.x Lollipop to one of the most-used screens you'll ever own.
The gist is this: Android Auto works by projecting a customized version of a compatible Android smartphone onto the in-car display after the phone has been plugged in to the car via USB. Phone calls are handled over Bluetooth. This opens up the possibility to use mobile apps behind the wheel such as Google Maps, Google Play Music, Google Now and third-party offerings (with modified interfaces for the car) such as MLB At Bat, Spotify and Pandora. The interface is very simple and adapted to be used with few taps and swipes — or even completely with voice control —while driving. It is primarily focused on media and navigation, with initial versions of Android Auto not being suited for climate controls or other in-car functions.
Underneath the hood Android Auto is just based on Android 5.0 Lollipop, with the same new Material Design language we're all getting used to. Some automakers have already confirmed their plans to support Android Auto, and several other manufacturers and third-party OEMs are releasing their own Android Auto-compatible head units. Pioneer released its new NEX series (the 4100, 5100 and 8100) in March 2015.