
When you connect the smartphone to the Car Audio via USB, SDL will display

When you connect an iPhone to the Car Audio via USB, Apple CarPlay is automatically initiated. You can use the audio/information screen, instead of the iPhone display, to make a phone call, Music, Maps, Siri and access Messages while driving.
Check below website to see How to use Apple CarPlay: https://www.apple.com/ios/carplay/

When you connect an Android phone to the Car Audio via USB, Android Auto is automatically initiated. You can use the audio/information screen to access the Android phone, to make a phone call, Google Maps, Music, Google Assistant and access Messages while driving.
Check below website to see How to use Android Auto: https://www.android.com/auto/

Application for control Car Audio by smartphone when pairing Bluetooth with Car Audio.
iAuto Remote Control can be downloaded on App Store and on Play Store