Block entity

A block entity (previously named tile entity) is extra data associated with a block, beyond the block ID and 4 extra bits of data that every block has.

Usage
Block entities store additional information about certain blocks, with the type of information varying by block, as well as schedule updates to perform each tick. In some cases, this information is used to create a more complex model, such as the book on an enchantment table. In other cases, it is used to store contents of an object. Additionally, blocks with block entities cannot be moved by pistons.

List of block entities
These are the current blocks which hold block entities.