Barrel

Barrels are block entities used to store items.

Natural generation
Barrels can generate naturally in fisher cottages in villages.

Container
Barrels have a container inventory similar to a single chest. They can be filled by droppers and both filled and emptied by hoppers. When broken, barrels drop the contents of the container and the barrel item itself.

Unlike chests, a barrel can be placed below a solid block and still be able to be opened.

Fuel
Barrels can be used as a fuel in furnaces, smelting 1.5 items per block.

Changing profession
If a village has a barrel and there is no fisherman villager in the village, any villager who does not have a chosen workstation has a chance to change their profession into a fisherman.‌

Block entity
A barrel has a block entity associated with it that holds additional data about the block.

Trivia

 * In Java Edition 3D Shareware v1.34, barrels render in 2D, are on fire, and spawn naturally within the world, containing random potions, tipped arrows, weapons and armor. Barrels will also explode when closed while empty or shot at.