I believe a soul is pure energy once released from our physical vessels and yes I believe souls have past lives except for people who are "soulless".
Our soul is something we as human beings have lost touch with. Spiritual knowledge used to be much like scientific knowledge thousands of years ago. It was something you could teach and progress at. Unfortunately the priests and rulers of humans have distorted this knowledge over the ages and turned it into theatrical rituals and the dogma of different forms of worship via the mystery schools and there "divine" exclusivity.
You should read The Gods of Eden by William Brambley. Don't be discouraged by the first couple of chapters because you will think "this is nuts". Keep reading.