Fairy

Fairies are very small and can fly. In some Zelda games they take the form of small orbs of light; in other games they take the form of tiny humans. They possess a great deal of healing power. Some fairies are assigned to Kokiri as their partners by the Great Deku Tree, while others stay in Fairy Fountains and wait for weary travelers.

Companions
In Ocarina of Time, Link is assisted by Navi, who helps keep him on track by reminding him where to go. She also helps him target objects and enemies, and can provide information about enemies.

In Majora's Mask, Navi is replaced by Tatl, a new fairy who serves the same purpose as his previous fairy.

Great Fairies
Great Fairies can power Link's items up, and are in many games.

A Link to the Past: The Great Fairy in the Waterfall of Wishing will power up your Shield and Boomerang. The Great Fairy in the Pyramid of Power will power up your Tempered Sword and your Arrows. Venus, the Queen of Fairies will allow you to hold more Arrows and Bombs.

Ocarina of Time: The Great Fairies' locations: Death Mountain, where you get the Magic Spin Attack, The path to Hyrule Castle, where you get Din's Fire, Zora Fountain, where you get Farore's Wind, Death Mountain Crater, where you get a Large Magic Meter, Desert Colossus, where you get Nayru's Love, And Ganon's Castle, where you get double Defense.

Majora's Mask: The five Great Fairies can be resurrected by collecting the Stray Fairies in the three days. they give you helpful items, such as a Magic Meter, and the Great Fairy's Sword.

Four Swords: After you beat each boss, a Great Fairy will speak to you, and if you and your friends performed well enough, she will give you one of the Great Keys.

The Minish Cap: Great Fairies are hidden throughout the land and upgrade your Quiver, Bomb Bag, and Wallet.