Furnace

"The main point of a furnace is to smelt things. Smelting requires fuel - usually coal or charcoal, and an object to be smelted. Pop those in the furnace and you'll see a progress bar for the smelting process which, when completed, yields a new object. Be careful which fuel you choose, because some are more efficient than others."

- Duncan Geere

A furnace is a block used to smelt blocks and items and convert them into other blocks or items.

Obtaining
Furnaces can be mined using any pickaxe. If mined without a pickaxe, it will drop nothing. A furnace will also drop when a minecart with furnace is broken.

Natural generation
Two furnaces can be found inside each blacksmith shop in villages, and one can be found inside each igloo.

Furnaces also generate in weaponsmith houses in plains villages, inside some houses in snowy tundra villages, in some desert village houses, and in taiga village houses.

Furnaces can also be found inside snowy tundra village house chests.

Crafting
The lit furnace block cannot be obtained in Java Edition, even with commands. In Bedrock Edition however, the lit furnace block can be obtained by inventory editing. It will always stay lit, despite no items being inside of it.

Usage
Furnaces cannot be pushed by pistons.

Smelting
The main purpose of furnaces is to allow for smelting. Its interface can be opened by on it.

Light source
Furnaces emit a light level of 13 when active, and emit smoke and flame particles.

Custom name
By default, the GUI of a furnace is labeled "Furnace", but this name can be customized by naming it in an anvil before placing it, or by changing the  tag using the  command.

Block data
In Bedrock Edition, furnaces use the following data values:

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

Trivia

 * Furnaces function as multiple devices combined into one block: bloomeries and blast furnaces (for smelting ores), an oven (for baking and cooking), a charcoal pit (for the charring of wood) and a kiln (for baking of clay).
 * Cats will often sit on top of active furnace