Small is a world type exclusive to the Console Edition, specifically to the Xbox One Edition and the Playstation 4 Edition.
Small world type selected in the World Options menu.
Small worlds generate finitely (due to the lack of infinite worlds in Console Edition), with an area of 1024×1024 blocks (1 Map). An endless sea of water preceded by an invisible barrier surrounds the edge of the world.
Small worlds are able to generate with any of the biomes (albeit at a reduced size) and generated structures available in the current version.
||Added the Small world type.
||Added World Resize option to expand smaller sized worlds into larger sized ones
Issues relating to “Small” are maintained on the issue tracker. Report issues there.