Event: Voucher
This event type lets you create reservations that aren't tied to a specific date or time. The customer creates a reservation, and it's then up to them when they use it (within the range defined by your settings).
Event: Voucher
more in the documentationUnlike other event types, the Coupon event type doesn't force the customer to choose a specific date and time to use the reserved services. The reservation only tells them the period during which they can use the service. That's exactly why this event type isn't suitable for services limited by capacity or a specific time – it doesn't let you set an overall capacity, because it isn't known in advance exactly when the customer will use their reservation.
This event type, or rather these reservations, are suitable anywhere you want to sell your services (typically in the form of tickets) while it doesn't much matter exactly when customers arrive, or what the limiting capacity is. Typical uses therefore include various exhibitions, zoos, historical sites, or various forms of access passes.