What is can box used for?
 

Anybody would like to explain whats a can box and what it is used for.

With so little context it's hard to be sure I am giving you the right answer.
Basically it's some sort of electronic box that interacts with the Car Area Network.

I am going to assume you are looking at adding an aftermarket stereo or navigation system. In this context it is mainly used to turn on the Rockford amplifier which is controlled over the CAN. If you don't have a Rockford audio system you probably won't need it for this purpose.

If you are asking about it in some other context you will have to elaborate where you heard the term and what you are trying to do.

It is a part of MMCS used for providing it with access to many systems, like AC mode or trip computer.
Not present on J-01.

I just want to know what it is for I have it in my car. Am seeing a slot for a card on it, what is the card for?

Vadimus I found out what the thing on my dash is, its a sensor used to see congestion ahead.