They are "TreeHouses". From what I understood, they have been there since around the time WDW opened and need some serious refurbishing, however, they are in protected wetlands and cannot be touched...cannot be torn down or refurbished. I believe they have one or two bedrooms, a master bedroom, a living area, etc. I believe the treehouses were a part of the resort that had something to do with "The Disney Institute", which has not been there in several years. I *think* they closed the treehouses when they closed The Disney Institute.
Hope that helps some...they usually told the story of the treehouses on the boat rides back and forth from DTD, but it's been a little over a month and I am not sure I remember all of the details.