Superflat

Superflat‌[JE only] or Flat world‌[BE only] is a world type or a vanilla world preset that replaces the normal varied terrain of the Overworld with a completely flat surface composed of multiple layers and set to a single biome.

A superflat world can be customized using presets, which change its layers and biome. In Java Edition, presets can also change the features and structures found in a superflat world, and an in-game menu allows players to fully customize the layers and the biome.

In Java Edition, superflat can also refer to a dimension's generator type, with which the completely flat terrain can be generated in a specific dimension. See also Custom dimension and Custom world preset.