Minecraft wiki entry for Mechanics, associated text: Altitude: A measurement of the absolute height of things in a Minecraft world.
Biomes: Different regions of a world with distinct topographic and environmental features, as well as flora and fauna.
Chunks: 16-by-16-block-wide areas that Minecraft uses to manage a world.
Coordinates: A measurement of the absolute, 3-dimensional location of things in a Minecraft world.
World seed: A string of characters or numbers, based upon which an entire Minecraft world is created.
World type: Determines whether the world generates by default, or in particular ways.