Minecraft is an mmo sandbox type of game where you can create and build anything you want to. Some people try to go the longest without dying which gets hard as animals and zombies attack you. But one of , if not the biggest part of the game is building a home. Homes are made for protection and you can even put traps into your houses a la Home Alone to stay alive and keep their homes from being destroyed. Many homes have moats around them for protection as well. Once you learn how to do everything you too can create your dream house.
These houses likely took many hours and days to complete, but the designs are awesome and really creative.