It lists your order modules (for example Meal Packs, Weekly Subscriptions, À la Carte, Catering, Extras, Products, Custom Meal Builder…) and decides which of them may be delivered to this zip code. At checkout, if the cart contains an item from a module that is not ticked for the matched zip, delivery is refused with Unfortunately we cannot process your item "<module>" using the Delivery method.

On a new zip all modules are ticked by default. In the list you can change them inline via the Allow To? column (a checklist); at least one module must stay selected there, otherwise you see Select at least a valid module.