The deal form explains both cases under “How this deal will work”.
- Without a code — the offer is simply shown on your listing. Anyone who sees it can ask for it. Good for “10% off on Mondays”.
- With a code — the visitor gets a code to quote. Good when you want to know where the customer came from, or limit who can use it.
The Discount Code field is marked optional, so leaving it empty is a deliberate, supported choice.