Sheikah Stone

Sheikah Stones are objects featured in Ocarina of Time 3D and Skyward Sword. These stones are similar in appearance to the Gossip Stones from Ocarina of Time, except that they are larger and their designs are often outlined with a bright, glowing color.

Appearances and Function
In every appearance, Sheikah Stones give Link visions and hints on how to solve puzzles, find secrets and defeat bosses on his adventure - provided he has reached a point in his quest close to accessing the subject.

Ocarina of Time 3D
In Ocarina of Time 3D, Sheikah Stones have a passage at the bottom for entry.

One Sheikah Stone can be found outside Link's house, and the other in the Temple of Time, presumably because these are the two potential starting points upon resuming a saved game. If Link talks to one, he will have the option to crawl inside it to bring up the Visions screen.

They are absent in the Master Quest version of the game.

Skyward Sword
Sheikah Stones in Skyward Sword appear closer to their Gossip Stone counterparts than in Ocarina of Time 3D.

After Link obtains the Practice Sword, a Sheikah Stone will appear and talk to Link outside the Sparring Hall. From then on, the young hero can summon a Sheikah Stone by playing the Ballad of the Goddess wherever a group of Blessed Butterflies appear.

If Link is playing in Hero Mode, the Sheikah stone will provide the young hero all of the hints upon their first encounter.

Trivia

 * If a bomb is thrown at the Sheikah Stone in Skyward Sword, it will blast off into the sky before exploding, and a new stone will emerge from the ground in its place.