The Eye of Horus (or Ra) is an ancient Egyptian symbol of protection by gods and royal power. They symbol is also known as wadjet (or wadjat, udjat or utchat).
It represents a peregrine falcon's eye and the markings around it, including the "teardrop" marking. It also represented the sun (The mirror image, or left eye, sometimes represented the moon and the god Tehuti or Thoth.) The ancients believed this symbol of indestructibility would assist in rebirth.