The Eye of Horus (Wedjat) (previously Wadjet and the Eye of the Moon; and afterwards as The Eye of Ra) or ("Udjat") is an ancient Egyptian symbol of protection and royal power from deities, in this case from Horus or Ra. The symbol is seen on images of Horus' mother, Hathor, and on other deities associated with her.
In the Egyptian language, the word for this symbol was "Wedjat". It was the eye of one of the earliest of Egyptian deities, Wadjet, who later became associated with Bast, Mut, and Hathor as well. Wedjat was a solar deity and this symbol began as her eye, an all seeing eye. In early artwork, Hathor is also depicted with this eye. funerary amulets were often made in the shape of the Eye of Horus. The Wedjat or Eye of Horus is "the central element" of seven "gold, faience, carnelian and lapis lazuli" bracelets found on the mummy of Shoshenq II. The Wedjat "was intended to protect the king [here] in the afterlife" and to ward off evil. Ancient Egyptian and Near Eastern sailors would frequently paint the symbol on the bow of their vessel to ensure safe sea travel. 
Horus was an ancient Egyptian sky god in the form of a falcon. The right eye represents a Peregrine Falcon's eye and the markings around it, that includes the "teardrop" marking sometimes found below the eye. As the wadjet (also udjat or utchat), it also represented the sun, and was associated with Horus' mother, Isis, and with Wadjet another goddess, as well as the sun deity Ra (Re). The mirror image, or left eye, sometimes represented the moon and the god Tehuti (Thoth).