What does these car audio terms mean? Need help with speakers etc?

I'm looking to buy my first set of speakers for my first car and I need help with a few of the terms used. If somebody could help me with the following it would really help. 1)What are the following pieces used for? -Amplifier -Sub Woofer 2)Also, what does peak wattage mean for a set of speakers? What... show more I'm looking to buy my first set of speakers for my first car and I need help with a few of the terms used. If somebody could help me with the following it would really help.

1)What are the following pieces used for?
-Amplifier
-Sub Woofer

2)Also, what does peak wattage mean for a set of speakers? What does wattage mean?

3)How do 1, 2 and 3 channel amplifiers vary?

4)Do I even need a sub in my car?

5)How can I tell how many speakers and at what wattage can I run off my head unit?

6)What's the difference between 2-way and 3-way speakers?

Thanks
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