Block Palettes define a vertical slice of the world. They are lists of blocks, from which Terra picks based on the depth
at a location. They are located in the
palettes/ directory within a config pack.
Palettes define the blocks used to generate the world, and they are configured on a per-Biome basis. Biomes contain a list of Palettes, based on Y levels, allowing the user to control which blocks generate at relative depths, and absolute depths.
Relative depth describes "distance below the surface." For example, a Palette can specify that 3 blocks below the surface of the world, Stone should generate.
Absolute depth is a Y-level. For example, a Biome can specify that at Y levels 0-96, a palette called GRASSY is to be used.
Palettes offer two types of randomness to use for block selection.