The waiting list is a list of reservations of rooms that are not (yet) available. Usually a reservation is put on the waiting list when no rooms are available for sale at the hotel for the requested dates.
To create a new waiting list reservation, see New waitinglist.
To convert an existing reservation to a Waiting List, see Move existing reservations to the waiting list.
To access the reservations already on the waiting list, use shortcut <Ctrl> + <L>, go to Reservations > Waitinglist:
Or use the Availability Screen by date. Double click on the number of rooms on the waiting list:
See Availability.
Reservations with a folio number that is lower will usually indicate that they were placed on the waiting list earlier.