This variable permits you to create a "caption" string for your room. If no caption is defined, or you wish to set no caption, use an empty string "".
NOTE: this variable is deprecated and may be removed in future versions of the product.
room_caption = room_get_name(room);
The above code will check to see if the room has a caption and if it does not it sets the caption to be the same as the name of the room.