'''Rooms''' can, but do not need to, represent ''physical'' rooms; they are a way of splitting your property into separately bookable units.
These units or "Rooms" could be guest bedrooms, hostel dormitories, individual beds in backpackers, camp sites, houseboats, holiday homes, individual hotel suites, cabins, tours, classes or cars etc.
If you're renting your property as a whole, you still need to define one "Room" which in your case represents your complete property.