1. GTY - When a certain percentage of rooms within a category have been booked, the category goes "GTY". You can still select that category, but you can't select a specific room. Your reservation will say for room assignment (for example) 9C GTY. You pay the same for a GTY reservation as you do for a reservation that has a specific room selected.
DCL will assign a room in that category or higher at a later date.
2. *GT - when a cruise isn't selling well, DCL will offer last minute restricted fares. These typically come out after the Paid in Full Date and you must pay in full, no refunds, or changes allowed. You book a TYPE of room (Interior - IGT; Oceanview - OGT; or Verandah - VGT). The price for these rooms, while generally lower than the prevailing rate is usually higher than the cost was had the reservation been made on opening day. DCL assigns these rooms at a later date.
OP - Original Poster (the person who started a thread).