A "head unit" is the central component of a car's audio system, typically located in the dashboard. It controls various functions such as radio, music playback, and navigation. Head units can connect to smartphones and other devices, allowing users to stream music and make hands-free calls. Modern head units often feature touchscreens and support for technologies like Bluetooth and Apple CarPlay. They can also include additional features like GPS navigation and USB ports for charging devices. Upgrading a head unit can enhance the overall audio experience and provide more entertainment options while driving.