Set this to true to enable a temporarily hold upon object selection.
If set to true, the user's browser issues a call to seats.io to hold the selected object for 15 minutes (or whatever you set on your settings page). Other users won't be able to book the same object within that period.
If the object is not booked (e.g. payment has never been received) within those 15 minutes, it's automatically released again.
This article gives a more in-depth overview of the holding seats functionality.