Jirachi is a small, white, humanoid Pokémon. It has short, stubby legs and comparatively longer arms. There are flaps on the underside of its arms, which give the impression of long sleeves. On its belly is a curved seam, which conceals a third, yellow eye with a cyan pupil, known as its "true eye". Additionally, Jirachi has a normal pair of ovalish eyes on its face, with small, blue triangular markings underneath. On its head is a large, yellow structure with three points extending outward: one from the top and one on either side. On each point is a teal tag, known as a "wish tag". A rounded extension hangs from either side of the yellow structure, framing Jirachi's face. Two yellow streamers flow from Jirachi's back, resembling comet tails.

Jirachi hibernates for most of its life, awakening for seven days every thousand years. It can be also awakened if sung to by a voice of purity. While it sleeps, a tough, crystalline shell envelops its body to protect it from enemies. However, it is still capable of fighting while asleep when its shell is not enough to protect it, as seen in Pokémon Mystery Dungeon. During the short periods when it is awake, Jirachi is said to grant wishes. However, in the movie Jirachi: Wish Maker (M06), Jirachi cannot create an object that is desired from a wish. Instead, it teleports the desired object to the person that made the wish. By contrast, in the Pokémon the Series: Black & White episode Searching for a Wish! (EP132), it displays the ability to grant wishes without the use of teleportation. In the Pokémon Adventures manga, Jirachi will only grant wishes when its true eye is opened. Additionally, it can only grant three wishes every thousand years, which are written on each of its three wish tags. In this canon, Jirachi is shown being able to create artificial Pokémon through its wishes, animating a mass of seawater in the shape of a Kyogre. Jirachi's power is similarly exploited in the movie to create a monstrous . The movie further reveals that Jirachi's awakening is linked to the appearance of the Millennium Comet and that its third eye has the ability to absorb the energy Jirachi needs for hibernation. It is said that Jirachi's ability to grant wishes also gives it great attack power, as seen when it creates a concentrated bundle of light to blast its target. Although it is extremely rare, Jirachi can be found in the mountains.

(Source: Bulbapedia)