In this universe, the soul consists of multiple energy types - Life Energy, Mana/Magical Power, Emotional Energy, Memorum, and Soul EssenceThere are others as well but they don't matter as much as the five main ones.
Life energy is the Soul's connection to the body. It's what keeps the soul bound to the body. It usually exists in large amounts in the human soul and also serves to keep the body functioning. A person's physical capabilities and health are usually connected to their life energy. Compare to a healthy fit person, a sickly and frail person has significantly less Life Energy. Life Energy can also be refined into what is commonly referred to as Ki or qi, which greatly raises the physical capabilities of a person. Life energy flows through the body via channels or "meridians" as described in Chinese medicine. Damage to the body usually causes damage to the meridians and thus has an adverse effect on the body's life energy.
As a person ages, their natural life energy generation becomes weaker, causing the body to weaken as well. When Life Energy has either been depleted or rapid loss occurs, such as from a major injury, the soul's connection to the body also weakens greatly. Once physical death occurs, the soul is released from the body.
Mana or Magical Power, a subset of Life Energy, is the spiritual fuel that allows the supernatural phenomenon that is magic to work. Every person barring a few extremely rare exceptions has a magic core, a spiritual organ within the body that works to link and manifest mana generated within themselves. A normal person has little capacity for magic due to lack of Magic Core usage. A mage on the other hand regularly exercises their magic core, thus allowing for growth through repeated depletion of their mana capacity. Due to their similarities, Mana can substitute for Life Energy if available in high enough amounts.
As a mage becomes more powerful and rises in magical strength, the ratio of life energy and mana within the body will grow to favor mana instead of life energy. A normal person will approximately have a life energy to mana ratio of 25 to 1 while an apprentice mage will have something more along the lines of 5 to 1. Once a mage's life energy to mana ratio tilts towards the mana side (eg 1:2), they can be considered no longer fully human. When Mana exceeds the amount of Life Energy within the body, it essentially takes on the functions of Life Energy with one exception. A powerful mage becomes capable of sustaining their physical existence even after the depletion of life energy within the body. Not only that, because the connection between the soul and body is altered, allowing a mage to separate their consciousness from their body if they are powerful enough.
Emotional Energy exists in all sentient beings. Emotional energy can be divided into positive and negative emotions. In order to function as a normal person, a balance of positive and negative emotional energy is needed. Postive Emotional Energy usually manifests as joy, interest, hope, confidence, kindness, satisfaction, optimism and so on. Negative Emotional Energy on the other hand often manifests as fear, anger, hatred, guilt, sadness, jealousy, anxiety and so on. Without one or the other, a person becomes distorted. Without fear, a person becomes reckless and do things without consideration of the consequences. Without hope, fear becomes despair leading down to spiral that ends in suicide. While emotional energy is not an integral part of the soul, it is needed in order to be alive instead of just merely existing.
Memorum is an energy that contains the soul's memories. Unlike the body's memory, the soul doesn't forget anything. However, the body's connections to Memorum can degrade over time if unused. Important memories usually continue to be linked to the body and be unlikely to be forgotten while trivial memories will have their connection to the body degrade due to insignificance and the likes. Memorum tends to get tinged in emotional energy due to their nature. The quality of Memorum depends on both the age of the memory as well as the importance it holds to the person. An important memory such as holding one's child for the first time would become high-quality Memorum especially if it is never forgotten. Fresher memories also hold better quality though importance usually takes precedent over age. Without Memorum, the body's memories degrade rapidly. After death, Memorum will slowly degrade as time passes. If a soul is left in the world for too long, a soul will eventually lose all their memories.
Soul Essense is energy that essentially acts as the glue that holds the other energy together into one coherent soul. Without it, the soul would deteriorate and dissipate into nothing. It is also what allows the soul to exist after physical death. Soul Essence grows in proportion to the sum of the soul's other energies - the more life energy, mana, emotional energy a person has, the greater soul essence they have as well, memorum is not included when defining the amount of soul essence the soul has. Due to its nature, soul essence is very valuable amongst mages and when a soul passes onto the after life, it leaves behind Soul essence that unless captured and stored properly will fade away on its own.
After the death of the physical body, the soul exists for a time after being released from its physical connection to the body. Depending on the potency of the remaining energy within the soul, the soul may become a ghost. Mages have a high likelihood of existing after death due to their mana. Certain souls may continue to exists thanks to particularly strong feelings and memories. A particularly Strong Soul Essence will also result in a spirit or ghost.