I haven't played Minecraft, but here's what I've learned about it. You start the game with nothing but a few tools and the clothes on your back. During the day you are free to cut down trees, mine ore, and gather any other type of building material you think you might need. At night, creepers come out (similar to zombies) and try to kill you. So the object is to build a shelter for yourself to keep safe at night. Technically a small shack with four walls and a door would be sufficient, but since you have a giant world to mine materials from, it becomes desirable to build something a little bit more extravagant. Due to the simple nature of the game (everything is cube shaped) and the wealth of different materials one can craft (wood, stone, glass etc.) building a sprawling metropolis is not only encouraged, it's addicting. While there really isn't any way to 'win' the game, the object is to build anything and everything your imagination can come up with. I know that the game has more objectives than this, but that's the gist of it.
