You are a thetan.
A long time ago, galactic dictator Xenu held a giant tax audit and kidnapped everyone and banished them to earth. They were spread out around volcanos, which errupted, and killed off the dinosaurs.
The thetans were highly traumatised, but they roamed around the earth and started picking up bodies. They are now trapped in this cycle of picking up bodies until those bodies die, and then picking up others, and will remain trapped in this cycle unless helped by the church.
Your body also has a thetan (a body thetan), and it has instincts and stuff, but you can overcome those (become "clear"). Once you are clear in the church you go on to learn more about Xenu and get over the trauma of the whole Xenu thing.
I was raised in the church of scientology, but am an atheist now.