It's just a preset with some ores, and etc, there is 30 layers of obsidian, mining these 30 layers down will lead to ore blocks (Like coal, iron, etc)

List of layers are shown on the screenshots

Preset: 10*minecraft:void_air,minecraft:bedrock,2*minecraft:netherite_block,2*minecraft:diamond_block,2*minecraft:lapis_block,2*minecraft:gold_block,2*minecraft:iron_block,2*minecraft:coal_block,2*minecraft:ancient_debris,30*minecraft:obsidian,minecraft:gravel,3*minecraft:obsidian,10*minecraft:emerald_ore,minecraft:deepslate_diamond_ore,minecraft:redstone_ore,minecraft:lapis_ore,minecraft:iron_ore,minecraft:coal_ore,10*minecraft:stone,2*minecraft:dirt,minecraft:grass_block,minecraft:oak_log,minecraft:air;minecraft:plains;village,stronghold,biome_1,dungeon