Maybe a stupid question but...

there's a few factors, some credit cards have a fee to use them - those are typically paid on a yearly basis if you do that at all (most starting out CCs are fee free) if you don't buy anything, or hold a balance over the month, there is typically no charge.

Correct. Pay the bill in full before the month is up and you'll get (almost) a month's free credit.

But don't cut the payment date too fine Because if you miss it, they'll hit you with a big "fine" as well as the interest on your month's bill.

It depends..if your credit card has monthly fees you may still need to pay something but typically no if you didn't borrow any money you don't have to pay anything back.

Yep. The secret is to pay back before the cutoff time for the monthly bill.

correct