What is the difference between Busch series and Cup series in Nascar?

I want to buy Nascar tix for a friend but I have no idea which one is preferable. We have Busch Dollar General 300 and Bank of America Cup 500 in Charlotte, NC. Which one would be what he wants?

What is the difference between Nascar and Formula1?

I have watched some races on TV but I do not understand the difference. I heard that the Nascar cars are heavier, Honestly I have no idea, so any help highly appreciated.

what is the difference between Nascar and Arca racing?

I know that they look very similar. I also know that Nascar has more races per season. How do the cars compare?
If you were a driver and had an opportunity to drive in Nascar or ARCA which would you choose and why? (forget about the prize money or exposure differences)

What is the difference between Sprint series and Nationwide in Nascar?

I’m brand new to nascar and I might go to the race next weekend but I have no idea what the differences in these series are… Can somebody explain this to me?