So the visuals are different in the car? I haven't installed my player yet. How are they different?

I don't know what gave you that idea. The visuals are the same in the car, they just aren't turned on by default. Every time you boot the player in the car, it switches to a text screen, which you can switch back to visuals yourself if you want. The reason for this is in the FAQ (although a moment's reflection should also tell you the reason).

And I don't really expect anyone to answer this ignorance question, but, what the hell is a shell?

In this context, it refers to the Linux command prompt.