Car stereo

A car stereo, also known as a head unit or car radio, is an essential component of any vehicle. 
Usage.
It is used to play music, make phone calls, and provide other audio services for the driver and passengers. Car stereos have many styles and sizes, with different features available depending on the model.
Types of car stereo.
Car stereos are typically divided into two categories: factory-installed or aftermarket. Factory-installed car stereos come with the vehicle and are usually of limited functionality, although some manufacturers offer premium systems that provide more features than standard models. Aftermarket car stereos are installed after the original purchase and can be customized to meet the driver's needs. 
Single-DIN stereos.
Single-DIN car stereos are the most common type of car stereo system. It refers to a standard size for radio and audio systems that measure 180 x 50 mm. They typically feature an AM/FM radio receiver and four pre-amp outputs for connecting external amplifiers and speakers.
Double-DIN stereos.
As the name suggests, these stereo are double in size and comes with standard size
(180 mm × 100 mm or 7.09 in × 3.94 in) and offers more features than a single-DIN unit. Now a days most of the double din stereo comes with a larger display (7 to 10 inches) that allows users to easily see and navigate the menus, make selections, and access various audio sources. These units often include built-in CD/DVD players, GPS navigation systems, Bluetooth connectivity, and even hands-free calling.
Double-DIN stereos also feature advanced audio processing, such as multi-band equalization, surround sound, and digital signal processing. Additionally, they often come with DVD players or navigation systems built-in. Double DIN radios also compatible with Android Auto and Apple CarPlay.