Minecraft wiki entry for History, associated text: The x index specifies the North to South location where a smaller value of x is farther North than a larger value of x. The z index specifies the East to West location where a smaller value of z is farther East than a larger value of z. The y index specifies the vertical location where a smaller value of y is at a lower height than a larger value of y. For an old style world, the block at the bottom of the North-East corner of the world is W [0, 0, 0].