Homes can be just one room or many.
A room needs some walls, a floor, and a ceiling. The simplest room design is four walls, a door, a single type of flooring, a plain ceiling and no built-in lighting, electrical, phone or cable outlets.
See the full set of rooms on the rooms category page. Some of the more common rooms are
Additional rooms in some houses are
Then there are "semi-rooms", that is, places in a building that might technically count as a room, but isn't usually counted as a room for measurement or real estate purposes. These "semi-rooms" include closets, hallways, storage places. (Note: In this wiki those are categorized as rooms for now.)
And there are external rooms or spaces, like