Will someone please explain a bit about how the classifieds work?

I can't tell, is it an auction or a but-it-now?

And this: "If you select to allow users to buy your ad you must set your paypal email address here" - If I select to allow user to buy my ad? Isn't that the reason I'm here? Or does that mean buy it now?

Thanks for any help you can offer
C

No auction. The price is listed and you just buy it for the listed price.