The wadjet, also called the Eye of Horus, means "the restoring eye". This is probably due to the myth where Horus lost his left eye battling with Seth. After plucking it out Seth shredded the eye and scattered the pieces. These bits were recovered by Thoth and reassembled, and the repaired eye was latter used to bring Horus's father, Osiris, back to life. It is said that the right eye, or udjat, represented the sun, and the left eye the moon, and this was why the moon waxes and wanes.
This symbol was said to ward off illness and evil, and have the power bring the dead back to life.