Moon

The Moon is a sprite that appears during night time.

Grass blocks or Saplings do not grow in moonlight unless there is a Torch (regular or Redstone) or other light source nearby, however they won't decay in moonlight either.

The moon illuminates topmost blocks during the night in the same way that the sun illuminates them in the day, but only illuminates them to a Light level of four, rather than the sun's fifteen.

The Moon is rather useful when looking for Constellations as it helps the player keep track of the sky.

Mobs
Hostile Mobs will spawn around dark areas of a normally generated map. When the moon is up, hostile Skeleton, Creeper, Zombie and Spider mobs will appear and attack the player. When the sun comes back up Skeletons and Zombies will burn in the sunlight and drop items after death. Spiders will not burn in daylight, but instead become neutral during the day, only to become hostile again if attacked, when it is night, or when it falls into a dark area. Creeper and Slime mobs do not burn, and will remain hostile during the day. (See also: Difficulty level)

Trivia

 * Night time lasts 7 minutes, plus 1.5 minutes each of sunrising and sunsetting.
 * You can't see the moon while using the short or tiny render distance settings.
 * The moon is 8 x 8 pixels.

Mond Луна