The ancient Egyptians believed the soul and the body of a person were linked, even after death. If the body decayed, the soul would be lost. Mummification kept them together.
The ancient Egyptians believed the soul of a person had three parts. The first was called the ka. It remained in the tomb after death, which is why so many items were buried alongside people in ancient Egypt. In the tombs of mummified Egyptians researchers have found jewelry, furniture, clothes, makeup, wine, food, animals and, in the case of kings, servants.
The second element of a person's soul was called the akh. It was the part of the soul that went on into the afterlife.
In ancient Egypt, the third element of a person's soul was called the ba. They believed this part of the soul could leave and return to the tomb as it pleased.
But the soul was not a formless entity according to the Egyptians. Instead, it needed the body to host it, which is why they went to such lengths to mummify the bodies of their dead. It was an expensive process though, so it was usually reserved for Pharaohs, and for rich and noble people in Egyptian society.
It was not only people that were mummified, either. Because of the religious beliefs held during the time of the Egyptian empire, some animals were also mummified.