Anubis was the god of mummification. Priests prayed to him and wore an Anubis mask while embalmers prepared a body for burial. He was shown as a jackal or as a man with a jackal's head.
Why a jackal?
Jackals are scavengers, meaning they eat animals that are already dead. They would have been seen around cemeteries looking for bodies to eat, so the Egyptians connected them with the dead. Jackals are actually brown, not black - black is the colour of a rotting corpse. Black also represents fertility, the colour of the mud left by the annual floods, in which farmers planted crops.
Anubis also led the dead souls to the weighing of the heart, and carried out the weighing himself (see right). This was to discover whether the dead person had been good enough to enter the afterlife.