The Ankh (anch) is, in the Egyptian hieroglyphic writing, the character for life. In Egyptian mythology it is a symbol of eternal life (hence immortality) and the universe.
The Ankh is probably one of the most important symbols of ancient Egypt and has been preserved as a sign to enter into Christianity. First the Copts took it over from the Egyptians and from there it passed into Christianity.
The Copts regard it as a symbol of eternal life, which was given to the people through the death of Christ.