The soul is eternal and indestructible, it always was and always will be and from time to time it moves from one body to another one as a temporary residence. Our body is vulnerable, the life span of a body is finite. Our body gets old and dies, but the soul is eternal and keeps being reborn in a new body.
Rebirth in practice
At the moment of death the body stops functioning. Heart, blood circulation and the activity of the brain stop. The body begins to slowly decompose. The soul gets separated from the physical body and spends some time to analyse the current life experiences and memories. Then it begins a new cycle of rebirth, in which a new mental and astral body is formed. Slowly the tasks of the soul determined by karma unfold, and these tasks will determine the new body (the abilities of this new body, etc.) which will enable the soul to fulfil the newly given tasks.
So, the main purpose of rebirth is the ongoing development of the soul and the ego through uncountable lives till the soul reaches the ‘perfect state’ when it can rest.
Reincarnation in East and West
The rebirth of the soul is the fundamental theorem and teaching of Eastern religions, but it seems to be completely missing from Western Christian doctrines. However, this impression is only formed at a cursory first glance. If you then study the Bible more carefully you can find references that the soul never dies, but is reborn.
This concept was denounced in Europe in the Middle Ages, even if the New Testament showed that Elijah was reborn as John the Baptist. And there is another reference in the Bible that the blind man is punished for his sins from his previous life (and his blindness was not caused by his parents). In early Christianity the theory of reincarnation was natural and accepted but later, due to the pressure of church leaders, this concept was denied and rejected.
Is there reincarnation at all?
This is real