The basic theory of reincarnation is the belief that the soul, after death, is reborn into a new physical body to begin a new life. The new body can be human, animal, or even spiritual, depending on the specific belief system.   An easy way to understand reincarnation is that it's the belief that the soul or life essence leaves the body after death and is reborn into a new one, like a continuous cycle of living, learning, and growing across different lives, often shaped by past actions, karma, to achieve spiritual perfection. Like a story where the main character changes costumes in different chapters to learn lessons until the story is complete.