Minecraft wiki entry for Pre-flattening, associated text: These data values refer to the different types of blocks and items on Java Edition. They are used in many places in Minecraft. Block IDs are used to define blocks placed in the world and inventory items (including items in chests and items dropped in the world). Item IDs are only valid for items. There are also Entity IDs for entities such as mobs and projectiles. Block data further defines blocks placed, describing for example the height of water or the direction a torch points.