A guide for newbies?

I understand that this is my first post, but take it for face value or not - I'm really interested in car audio and I want to know the mechanics behind it all.

Just the basics, you know? I know that an Ohm is a unit of electrical resistance, but from what? What of voltages and amperes?

If it isn't too much to ask.

 

here is a good one i've seen linked a number of times.
Basic Car Audio Electronics