This is not an endorsement of Scientology or a recommendation to get involved with Scientology. In fact since my involvement with Scientology was in the early 80's, when L Ron Hubbard was still alive, I have no ideal what the contemporary experience of Scientology would be.
I posted this in the religious debate section because I intent to explain my theory of how/why Scientology works. So feel free to ask questions or disagree with my beliefs.
My Scientology credentials, as mentioned, I joined in the early 80's. I was introduce to Scientology through the "Personality Test". This was the normal recruitment process. They get you to agree to come in, take a personality test. Give you a personality evaluation and then try to convince you to take some training courses. They were called TR0 through TR4 I believe. TR means training routine. This are basic courses that train a person to become an auditor.
An auditor is a person trained to lead an individual through a series of processes created by L Ron Hubbard with the intent of removing "engrams" that occurred during one's current lifetime. Events which cause mental aberration in one's personality. The end goal being to "Clear" an individual of all of these engrams so they can be mentally healthy.
The purpose of the TRs is to train you to not emotional react to what others individual say or do. During auditing you may hear of terrible things done by or to an individual you are auditing. You are not allow to react to anything said or done by the individual during auditing. You must complete the auditing process as written without interruption for it to work. You can't allow yourself to be sidetracked by the auditee.
There are two basic tracks in Scientology. That of auditor and that of the auditee. Either you pay for the training to audit others or you pay to be audited by others. There is also a third route through Scientology, the route I took. That of joining the Sea Org. You sign a million year contract and to work for Scientology and then both training and auditing is free, as long as you don't leave. Otherwise you owe all of that money for any auditing and training you received.