Shield

A shield is an item in the Legend of Zelda series that allows Link to block certain attacks from hurting him. The first shield in the series was the Magical Shield from The Legend of Zelda. The most recent is the Ordon Shield from Twilight Princess.

The Legend of Zelda, The Adventure of Link, an A Link to the Past
The first shield ever used by a boy named Link was in the 1987 game, The Legend of Zelda. In it, Link automatically started the game with the shield. In this game, Link blocked attacked with his shield if he wasn't using an item or his sword. In the sequel, Zelda II: The Adventure of Link, Link used the shield the same way, it would reflect attacks only if you weren't using items or your sword. The trend continued into the Super Nintendo with The Legend of Zelda: A Link to the Past.

Link's Awakening, and the Oracale trio
Link made his debut on the Game Boy with The Legend of Zelda: Link's Awakening along with a new shield setup. You acquired the shield from the people who rescued you on the island you were stranded on. Also, the shield was used when you held the button the shield was assigned to, therefore allowing certain situations where Link didn't wear his shield his at all. This trend continued in the Oracle Games (The Legend of Zelda: Oracle of Ages and The Legend of Zelda: Oracle of Seasons)

Ocarina of time, Majora's Mask, AND The Wind Waker
Into the world of 3D, Link once again changed his shield setup. In the acclaimed game The Legend of Zelda: Ocarina of Time, the shield was bought at the beginning of the game and was used when you held down the R-Button. If you used the shield as is, Link would crouch and block attacks in that stance. If the shield was used with Z-Targeting (and later L-Targeting), Link was able to move around while blocking attacks. This system was also used in The Legend of Zelda: Majora's Mask. In the Gamecube game The Legend of Zelda: The Wind Waker, the same system was used, however, the buttons were rearranged. Z-Targeting became L-Targeting, but the shield remained on the R-Button.

In The Legend of Zelda: Twilight Princess
Link first receives the Ordon Shield during his first trip in Ordon Village as a wolf. Link can keep the shield raised when he L-Targets, as opposed to using the R button in previous games. Later, Link can learn the Shield Attack from one of the Golden Wolves around Hyrule. Like the Deku Shield in Ocarina of Time, the Ordon Shield burns after catching fire. The Hylian Shield can be purchased from Malo Mart in Kakariko Village.