Lantern

Lanterns are blocks that emit light.

Natural generation
Lanterns can generate as lamps or lamp posts above farms and on some buildings in snowy tundra villages.

Trading
Apprentice-level Librarian villagers have a 50% or $2/3$ chance of selling a lantern for an emerald as part of their trades.

Usage
Lanterns can be placed on the top or hanging under most solid blocks, although some require. More information can be found at Opacity/Placement.

Light
Lanterns give off a light level of 15, which is one level higher than torches. They also melt snow layers within 3 blocks and ice within 3 blocks.

Trivia

 * Lanterns were likely to be a "replacement" version of the torch if they were added in the 2010 Halloween Update.
 * Lanterns are the fifth animated light-source in the game, the others being magma blocks, sea lanterns, fire and lava.
 * When gravity affected blocks, such as sand, are dropped on lanterns, they break as if they were dropped onto torches.
 * $$, lanterns are called sea lanterns.