Side Quest

Side Quests are found in the majority of the games in the Legend of Zelda series. A side quest is generally described as a course of action which Link can follow in order to achieve a particular goal; the action is not usually required in order to finish the game, but will provide him with a useful item, information, or something else which will in some way enhance his performance.

The Legend of Zelda
In the original game in the series, there is only one side quest -- the collection of Heart Containers. This is necessary in order to finish the game, as the Magical Sword is required in order to defeat Ganon, and cannot be claimed until Link has at least twelve Heart Containers. In the subsequent games in the series, Link collects Pieces of Heart, which fuse themselves into Heart Containers; the original game is the only one in which a specific number of containers must be achieved before Link can acquire a necessary item.

The Legend of Zelda: Link's Awakening
On Koholint Island, Link has the option of collecting Secret Seashells, items hidden all over the island. If he collects at least twenty, he can then go to the Seashell Mansion and have his sword upgraded from "L1" to "L2," making it stronger and more powerful.

The Legend of Zelda: Ocarina of Time
In this game, Link can perform the Happy Mask side quest, which requires him to collect a series of masks. Once he has completed this quest, he will be allowed to borrow the Mask of Truth, which allows him to hear and understand the whisperings of the Gossip Stones.

The Legend of Zelda: The Wind Waker
In The Wind Waker is the Savage Labyrinth a secret cave with 50 floors, filled with minions of Ganon. The first eleven floors are required, as Link must get the Triforce Chart found on the eleventh floor; from there he can escape if he chooses. If he completes the entire labyrinth, he is rewarded with a Piece of Heart.

The Legend of Zelda: Twilight Princess
There are three side quests in Twilight Princess which Link may choose to perform. None of them are required.

The Bug Collection -- Link can collect pairs of Golden Bugs for Agitha, the self-titled Princess of the insect kingdom. She will reward him for his findings with larger bags in which he can carry greater amounts of Rupees.

The Poe Quest -- Link will encounter a gentleman named Jovani, a Hyrulean who was turned into a gold statue through his greed. If Link will find and defeat sixty Poe Souls, Jovani will be restored to his human self and will reward Link with 200 Rupees.

Cave of Ordeals -- The Cave of Ordeals is a 50-room mini-dungeon. Most of the rooms are filled with enemies; however, every time Link fights his way through ten rooms, he will achieve the restoration of fairies to the four springs in Hyrule belonging to the Light Spirits; thereafter, he can visit the springs at any time and have his health replenished. If he completes the entire cave, he is rewarded with Great Fairy Tears.