In Egyptian hieroglyphs, the Ankh (anch) is the character for 'life.' In Egyptian mythology, it is a symbol of eternal life (and thus immortality) and the universe.
The Ankh is arguably one of the most significant symbols of ancient Egypt and has survived as a sign well into Christianity. It was first adopted by the Copts from the Egyptians, and from there, it found its way into broader Christian tradition.
The Copts view it as a symbol of the eternal life granted to humanity through the death of Christ.