[m0nk1337]

This is a post which will cover basic things which a car contains and how they work.
A car is basically a network which contains multiple computers(we can say) which are called ECU (Electronic Control Unit) used to control door locks, windows, engine, performance, transmission, multimedia player, wifi/bluetooth devices, lights and other things. Each of the things have their own ECU for example when you press or pull window buttons the ECU for windows sends a command to the network and depending on which button is pressed/pulled windows on the car acts. An ECU can also be connected to multiple networks.

Generally a car contains 2 networks :
For critical data such as data sent to engine/transmission and performance related.
And one for not so critical data such as radio, multimedia player, calls, navigation, door locks etc.

There can be more than 2 networks in a car as well.

How do these things communicate?
Just like any other network, the networks inside a car also communicate over ports/protocols depending on type of data like to send critical data it uses some fast protocols and for non-critical data it uses slower protocols. The protocols are listed below :
CAN Bus
SAE J1850
Keyword Protocol
Local Interconnect Protocol
MOST Protocol
Flex Ray Bus
Automotive Ethernet

Okay! great, But how can we connect to a network inside car?
There is this interface named OBD-II which stands for On-Board diagnostics which can be used to connect to the network of a car and can be found beneath the steering wheel so that driver's hands can reach it easily. OBD-II has became necessary around the world now, specially in india it became mandatory since April 1 2020.
OBD-II allows 5 signaling protocols and completely depends upon the car manufacturer which one to use, but most of the manufacturers use CAN and CAN is the most popular for speedy data transfer specifically used to send critical data.