Jars can hold all kinds of good stuff: cookies, jelly, fruit...human internal organs.
In ancient Egypt, important people would be mummified before being put into their tombs. Naturally, they'd need their "ba" to live in the afterlife, or their "ka"might have to wander the earth as a ghost forever. As part of the mummification process, the internal organs would be removed and prepared separately. From a cut in the side of the body, the priests would take out the liver, the lungs, the stomach, and the intestines. After being dried in natron (salt and baking soda), the organs would be placed in specially prepared jars called canopic jars.
The canopic jars would have been placed in a separate chamber of the tomb for the pharaoh's afterlife. Each canopic jar had the head of a different god, considered a protector of that particular organ. The four gods are considered the Four Sons of Horus. Horus was the god associated with the pharaoh, and was himself a son of Osiris, the god of the underworld.The Sons of Horus are also associated with the four compass directions: North, South, East, and West.
Imsety: The Liver
Imsety is unique among the Four Sons of Horus, and among the canopic jars, as the only one with a human head. Imsety's job was to revive the dead mummy (by magic).
Duamutef: The Stomach
Duamutef is depicted as a jackal-headed god much like Anubis. Duamutef's job is to worship the dead pharaoh in the afterlife.
Hapi: The Lungs
Hapi was a baboon-headed god who was associated with speed, and perhaps the steering of boats.
Qebehsenuef: The Intestines
Qebehsenuef was a falcon or hawk-headed god whose job was to refresh or give water to the dead pharaoh. He was associated with reassembling the dead person, just as Osiris was reassembled after his brother Set chopped him up.