Block entity

Tile entities are additional data for a block, beyond the block ID and 4 bits of so-called metadata that every block has (as described in the data values article). In addition, tile entities are able to perform an action each tick.

The blocks which have tile entities are:
 * Signs, to store the text to be displayed.
 * Chests, Dispensers, Furnaces and Brewing Stands to store their contents. Furnaces also store the time until the current item is smelted, and the time until the furnace's current fuel item is exhausted. Brewing Stands also store the brewing time.
 * Monster Spawners, to store which mob will be spawned and the time until the next mob is spawned.
 * Note Blocks, to store which note will be played.
 * Blocks being moved by pistons, to store the offset of block, direction of movement, and ID of moving block.
 * Jukeboxes, if and which music disc is inside
 * Enchantment Tables for the floating book.