Minecraft is a building gaming software, where you can build anything. Modular shapes are used to create this house structure. You can even see that environment around the house has been built and designed using modular shapes.
This is a large castle, and is a nice, very late-game house. The grey represents what material you want to make it out of and (not including floors) is approx. 40 stacks of material for an 10 block high, one floor castle.