The ankh is the ancient Egyptian symbol of eternal life. According to The Egyptian Book of Living and Dying, the ankh is representative of the key to life.
One theory is that the loop at the top symbolizes the rising sun, the horizontal bar represents feminine energy, and the vertical bar indicates masculine energy. Together they combine to form a symbol of fertility and power. Other ideas are far more simple - that the ankh is a representation of a sandal strap. Some researchers have indicated that it was used as a cartouche of a king's name, and others see it as a phallic symbol, due to its shape and structure. Regardless, it is seen universally as a symbol of life everlasting, and is often worn as a symbol of protection.
The ankh is featured on funerary artwork, in temple carvings, and in reliefs excavated from ancient Egypt. It is traditionally drawn in gold, which is the color of the sun. Because the ankh is a powerful symbol -- and because Egyptian influence spanned far beyond the country's original borders -- the ankh has been found in many places other than Egypt. Rosicrucians and Coptic Christians used it as a symbol, despite the fact that it was shrouded in mystery for centuries. Even Elvis Presley wore an ankh pendant among his other jewelry!
Today, many Kemetic recon groups and devotees of Isis invoke the ankh during rituals. It may be traced in the air to delineate sacred space, or used as a ward against evil.