The concept of three souls is something that can be found in the ancient belief system of all people who have spoken Uralic languages. The idea is that outside our physical body people had two other souls.
Ruumissielu / the body soul
The first soul for the ancient Finns was body soul ruumissielu/löyly. Löyly was all the functions of the body. Like the heartbeat and breathing. It was believed that person was born into their body soul from the first moment when they caught their breath to the day they died and took their last breath. Similar words to löyly can be found from different Finno-Ugric languages. In Hungarian löyly is lelek which means both spirit and soul. In Estonian löyly is leil and it means life and spirit. In northern Saami word, liewl means spirit, steam, soul and breathing. In Komi language word lol means soul and life. Ruumissielu the body soul was attached to the person´s body and when the body soul left then the person would die. (In modern Finnish language löyly refers to the steam that rises when you throw water into the sauna stove).
Itse, The Self
The second soul was itse the self. Itse is closer to the concept of the psyche and it was also known as vapaasielu the free soul. Itse was the persona, the identity of the person. There were many ways itse could attach itself to the body. It was believed that itse would become part of the person when the child was accepted as part of the family. This usually happened during the naming ritual. The concept of itse was tightly connected to the family and the community. For example among the Saami people child who had a name also had the right to own reindeers.
The concept of the three souls is connected to the belief in re-carnation. People often named their children after their ancestors and passed away relatives. There was a belief that the ancestor´s itse would reincarnate itself in the child. Unlike löyly which was always connected to the body, itse could leave the body and come back. For example, during nights when the person was sleeping their itse might go out and return the next morning. This is why it was forbidden to suddenly wake up a sleeping person. Their soul might not have returned just yet. If itse would not travel in the dream world or in other realms person who lost their itse got very ill. The only person who could bring their soul back was the shaman. Shamans were the only ones whose itse could travel in the underworld within the trance state.
Haltija-Sielu /Guardian Spirit
The third soul was haltija (also sometimes called luontohaltija). Each person was believed to have their own haltija, an invisible guardian spirit who would look after the person. Some people were believed to have extremely strong haltija, especially if they were successful in their lives. A person who was not so successful they were believed to have very poor and weak haltija. Haltija could also aband the person if they thought they were not worthy of them. Luonto in Finnish means nature and also refers to the nature of the person. An aggressive person might have shorth-tempered haltija when a kinder person had a very good-willed haltija.