Block entity

A Tile entity is extra data associated with 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. Tile entities are detailed in the Chunk format page.

The blocks which have tile data are:
 * Signs, to store the text to be displayed.
 * Chests, Dispensers, Furnaces, Brewing Stands, Hoppers, Droppers and Beacons 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, additional data about the mob to be spawned, the time until the next mob is spawned, the min and max values for the next spawn delay, and how many mobs to spawn per spawn attempt.
 * 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. Note that pistons cannot move other blocks with tile entities, as they would have to store that block's tile entities otherwise.
 * Jukeboxes, if and which music disc is inside.
 * Enchantment Tables, for the floating book.
 * End portals and Ender Chests, for the particle field effect.
 * Heads, for the type of the head and optionally the player represented.
 * Command Blocks, for the command used.
 * Nether Reactor Cores, to store whether the reaction started and the time remaining in the reaction.