Chunks are the basic unit of data storage in Minecraft. They are cuboid regions of the world that are 16 blocks wide, 16 blocks long, and 256 blocks high. Chunks are used to store the terrain, blocks, and entities in the world.
Chunks are generated as the player explores the world. When a player enters a new chunk, the game generates the terrain and places blocks and entities in the chunk. Chunks are also used to store changes made to the world by the player, such as when the player builds a house or digs a hole.