Construction of the Image:
The ankh is an oval or point-down teardrop set atop a T shape. The origin of this image is highly debated. Some have suggested that it represents a sandal strap, although the reasoning behind such a use is not obvious. Others point out the similarity with another shape known as a knot of Isis (or a tyet), the meaning of which is also obscure.
The most commonly repeated explanation is that it is a union of a female symbol (the oval, representing the vagina or uterus) with a male symbol (the phallic upright line), but there's no actual evidence supporting that interpretation.
The ankh is generally displayed in association with the gods. Most are found in funerary images. However, most surviving artwork in Egypt is found in tombs, so availability of evidence is skewed. The gods involved in the judgment of the dead may possess ankh. They may carry it in their hand or hold it up to the nose of the diseased, breathing in eternal life.
There are also funerary statues of pharaohs in which a ankh is clutched in each hand, although a crook and flail – symbols of authority – are more common.
Pharaoh Akhenaten embraced a monotheistic religion centered on worship of the sun disk, known as the Aten. Artwork from the time of his rule, known as the Amarna period, always include the Aten in images of the pharaoh. This image is a circular disk with rays terminating in hands reaching down toward the royal family. Sometimes, although not always, the hands clutch ankhs.
Again, the meaning is clear: eternal life is a gift of the gods meant most specifically for the pharaoh and perhaps his family. (Akhenaten emphasized the role of his family much more than other pharaohs. More often, pharaohs are depicted alone or with the gods.)
Was and Djed:
The ankh is also commonly displayed in association with the was staff or djed column. The djed column represents stability and fortitude. It is is closely associated with Osiris, god of the underworld and also of fertility, and it has been suggested that the column represents a stylized tree. The was staff is a symbol of the power of rulership.
Together, the symbols appear to offer strength, success, longevity and long life.