World type

World Type is an option for World Generation first introduced in Snapshot 12w01a. It allows the player to create worlds of specific type as provided. It currently offers the types Default, Superflat, and Large Biomes.

Default

 * This was the only available world type until the release of Minecraft 1.1, adding Superflat worlds.
 * The first World Type.

Superflat

 * In Superflat World type, the Void appears sky color from above Y coordinate 0. However, when viewed from below this coordinate, the Void appears its normal black color.
 * Slimes are very common on Superflat worlds, as the ground level is only 4 blocks above the bottom and slimes spawn from layers 40 to the bottom.
 * Villages spawn rates are somewhat increased when using this world type.
 * In Superflat the Nether and the End generate normally.
 * In Xbox 360 Edition, the Nether generates superflat as well.

Large Biomes

 * The world is generated like normal, only biomes are 4 times bigger linearly (16 times by area).
 * When comparing a normal and Large Biomes worlds with the same seeds using a map, the Large Biomes world looks like a zoomed in version of the Normal world.
 * Rivers are not larger than they are in Default.

Skylands

 * It is an upcoming feature as of 1.7 and 1.7.1.