. . are expressions of a composite entity. They are created and absorbed back similarly to how your body (a composite entity) creates cells and absorbs them back. In this way the composite entity gains experience and capability.
To some ways of thinking this composite entity is your personal God - but not likely the ultimate God.
It is not, of course, possible for us to comprehend the nature or purpose of the composite entity or the reality in which it exists. It probably has just as much trouble comprehending those as we have comprehending our own, and as our individual cells have dealing with their own environment.
It is also impossible to know to what degree our existence may continue after absorption, or whether fragments of our existence may be incorporated within subsequently generated souls - but reincarnationists say some of it is.