Relationship between past lives and reincarnation?

They are part of that process. You can not talk of past lives without talking about reincarnation and vice versa. The term
Reincarnation has different meanings for each person. It is a theory, a philosophy, a belief system and way of life. Provides an explanation about the inequities and suffering. It allows us to better perceive our many individual differences.
More importantly, the reincarnation provides a model of behavior based on the life and personal responsibility.

Literally, it means a return to the reincarnation physical body. It is the belief that the soul at the time of death, leaving a body and begins to prepare to return to life with another physical form. The circumstances of that return, the environment and others are determined by the growth and progress achieved in previous lives.

Each personality that is acquired is a synthesis of what has happened before, and the renaissance is presented in an environment that allows the individual to develop and evolve, so you can maximize profits.