What are we?
By essence, we are a spirit, a ball of divine energy endowed with intention. This energy has a vibration that is more or less high, corresponding to the spirit's level of consciousness. Furthermore, this spirit is clothed in a soul, a wonderful element that allows it to experience emotions and thus grow. Additionally, the soul enables incarnation in the material world.
It is the soul that enables elevation: inhabiting a physical body is a great honor as it offers the possibility to store a wealth of information in the form of perceptions, sensations, and emotions. This extremely rich experience teaches a lot and helps elevate the spirit.
Incarnations
Incarnation allows beings to form bonds, bonds of learning. Thus, as long as these bonds exist, the spirit must return to a body to complete its relationships. Life after life, we encounter the same beings in different roles within the family and among loved ones. Your brother from one life may become your best friend in the next; your parents might become your children, your nephews, or a partner…
But be careful! Incarnation also carries dangers. The heavy nature of matter lowers the vibration of the spirit and exposes it to experiences that can lower it even further. Negative emotions resulting from painful experiences can reduce the vibration to the point where the spirit may explore dangerous paths (violent lives, harm, drugs). If the spirit lowers its vibration too much through abominable practices (massacres, cruelty, and forbidden practices), it may lose its soul. From then on, it is no longer able to incarnate and stagnates in very low vibrations. This is an unpleasant fate, but fortunately, it is rare.

Most of the time, the spirit elevates itself through its lives. Once its vibration is high enough, the spirit no longer needs to incarnate. It becomes awakened and gains access to higher planes of existence (beyond the mental plane). However, it may choose to return to the material world again to help others grow. This gift is very generous because the awakened spirit must then bear the heavy energies from which it had previously freed itself and take the risk of being exposed to them once more.