It defines whether a catering order may or must be tied to a venue:

• Optional (default) - customers can add a venue to a catering order or skip it.
• Mandatory - a venue must be part of the catering order.
• Not Allowed - catering items and venues cannot be combined; if a customer tries to add a venue to a date that already has catering items, the cart refuses with Catering Is Not Allowed On Venues.

Venue availability is also checked against the catering start/end times chosen for the date when Allow Venues is on.