Chunk

A method used by Notch to divide infinite maps in the alpha release. They are 16*128*16 blocks. When wandering the world the nearest 81 chunks are loaded, arranged in a 9 by 9 grid around the player. These chunks may have activity (mobs spawning, trees growing, water flowing, dropped items disappearing etc. etc.), while the other world chunks are stored on your hard drive. If a player was to go to an area that is beyond the already generated chunks, new chunks will be generated and stored to the drive.

Chunks