What is Minecraft? Minecraft is probably best described as a sandbox game. You start the game, in the middle of nowhere, your goal? Well, there is no real goal, you can't 'win' in Minecraft, you can only play, and explore.
Basically, you collect resources like wood, stone, coal and iron, to make tools, with tools you can collect even more resources even faster, and before you know it, you've built a huge fortress with a huge-ass mineshaft down to the bottom of the earth.
The awesome thing about Minecraft, is that the maps are always randomly generated, you could begin the game next to a mountain, or on a small island, either way, there's plenty to explore, 'cause the maps can be up to 8 times as big as the Earth's surface.
Yes.
8 times the surface of Earth.
The game's currently in Alpha, so there's still a number of items and stuff that don't really have a use yet, but updates constantly add new items and fucntions to the game.
Oh and the graphics just make it more awesome.
Minecraft Flight
Video showing off teh awesome map generator