Deity

The Deities are the most powerful and important creatures in the worlds of The Legend of Zelda series. They have created the world and all the realms it holds. They also created life and sometimes, a specific race (though it is unknown who did what). In general, Deities can be divided into the higher Deities (gods) and the lower Deities (spirits).

Gods
The first group, the gods are the ones who supposedly created the world in the first place (though it should be noted there already was something before they came) and caused life to exist. It is unknown where they came from or for how long they have existed. Only three gods are known in The Legend of Zelda: the Three goddesses. Din, Nayru and Farore) are portrayed everywhere as three beautiful young women with enormous powers who reside in the heavens. They are the only known, or rather, specifically mentioned Gods in the games. However, at a number of times other goddesses are referred to. For example, in The Legend of Zelda: Ocarina of Time, the Gerudos worship the Sand Goddess; in The Legend of Zelda: Majora's Mask, both Princess Zelda and Tatl mention the Goddess of Time very early in the game. The Legend of Zelda: The Wind Waker featured the Tower of the Gods rather than the Tower of the Goddesses, and also Cyclos and Zephos are referred to as the wind "gods". Also, Zant wasn't surprised to see a "god" other than the Three goddesses. If there are more gods, it is unclear what their role is in the affairs of Hyrule and the other countries and dimensions. The gods don't seem to meddle too much with what is going on in the world of the mortals, although it seems they do extreme things (choosing a hero, flooding Hyrule) once in awhile if their creation is threatened. On The Legend of Zelda: Majora's Mask, Link gets a mask that transforms him into Fierce Deity, a god of fury.

Spirits
Spirits on the other hand, may not be as powerful as gods, but are still powerful enough to create worlds and creatures. This is shown in The Legend of Zelda: Majora's Mask, in which the Four Giants supposedly created Termina (the land, not the realm or the rest of that world). And it was the Great Deku Tree who, according The Legend of Zelda: Ocarina of Time, created the Kokiri. Unlike the Gods, the Spirits live with the other races on earth, instead of watching them from a distance. They sometimes act as a leader or second leader for a population of their chosen race and are always treated with a huge amount of respect. Spirits differ greatly in appearance, though they are usually very big and most of them resemble an animal. The Great Deku Tree on the other hand resembles a tree and the Four Giants of Termina look like clay heads with very long legs and arms. It is unclear if they can influence their appearance. Spirits age and can be killed (and seem to be able to die from old age), though they also appear to reincarnate as their own offspring (as is shown by the Great Deku Tree) in case they die, with their full conscience and memory intact. Spirits don't really form a society. Though they seem to know of each other, they usually don't interact as they rarely leave their territories. Rather, they are part of the society of another race or live alone somewhere. Also, it is unknown if all Deities are good or at least neutral. Some of the dungeon bosses could easily be Spirits as well, though that is not confirmed. In The Legend of Zelda: Twilight Princess, four light spirits (Ordona, Faron, Eldin, and Lanayru) have been subdued by Zant, who reverted their respective provinces to twilight. Wolf Link had to fill the Vessel of Light with 20 or so Tears of Light found inside of the Twilight Insects. Once this was completed, the land would be returned into light and the spirit revitalized. At the end of the game, they granted the plea of Princess Zelda and gave her Light Arrows to stun the riding Ganondorf so Link could slash at him with the Master Sword. Also, the Spirits of Good are the protectors of New Hyrule.