Scientology is based on the idea that our souls are weighed down by engrams, which form from trauma. Thus, the practices of Scientology focus on avoiding the formation of engrams as well as releasing the ones already formed (generally though a process called auditing).
More quick info here:
http://altreligion.about.com/od/alternativereligionsaz/a/scientology.htm
A silly set of beliefs based on a book from L Ron Hubbard that says we are immortal spiritual beings who have forgotten our true nature. The goons who came up with that are laughing at idiots like Tom cruise all the way to the bank.
Scientology is a "religion" made up by a sci-fie author. It is complete nonsense, and is merely a scam designed to get people to give more money to those who are at the very top of the scatologicalALierarchy.
For more information, see http://en.wikipedia.org/wiki/Scientology
They believe that 75 million years ago, there was an alien galactic ruler named Xenu who was in charge of 76 planets in our sector of the galaxy, including planet Earth, whose name at that time was Teegeeack. All of the planets Xenu controlled were over-populated by, on average, 178 billion people. Social problems dictated that Xenu rid his sector of the galaxy of this overpopulation problem, so he developed a plan. Xenu sent out Tax Audit demands to all these billions of people. As each one entered the audit centers for the income tax inspections, the people were seized, held down and injected with a mixture of alcohol and glycol, and frozen. Then, all 13.5 trillion of these frozen people were put into spaceships that looked exactly like DC8 airplanes, except that the spaceships had rocket engines instead of propellers. Xenu?s entire fleet of DC8-like spaceships then flew to planet Earth, where the frozen people were dumped in and around volcanoes in the Canary Islands and the Hawaiian Islands. When Xenu?s Air Force had finished dumping the bodies into the volcanoes, hydrogen bombs were dropped into the volcanoes and the frozen space aliens were destroyed. However, Xenu?s plan involved setting up electronic traps in Teegeeack?s atmosphere which were designed to trap the souls or spirits of the dead space aliens. When the 13.5 trillion spirits were being blown around on the nuclear winds, the electronic traps worked like a charm and captured all the souls in the electronic, sticky fly-paper like traps. The spirits of the aliens were then taken to huge multiplex cinemas that Xenu had previously instructed his forces to build on Teegeeack. In these movie theaters the spirits had to spend many days watching special 3-D movies, the purpose of which was twofold: 1) to implant into these spirits a false reality, i.e. the reality that WOGS (Hubbard?s derisory term for anyone not a Scientologists) know on Earth today; and, 2) to control these spirits for all eternity so that they could never cause trouble for Xenu in this sector of the Galaxy. During these films, many false pictures were implanted into these spirits, which resulted in the spirits believing in all the things that control mankind on Earth today, including religion. The concept of religion, including God, Christ, Mohammed, Moses etc., were all an implanted false reality that to this very minute is used to control WOGS on Earth. When the films ended and the souls left the cinema, they started to stick together in clusters of a few thousand and remained that way until mankind began to inhabit the Earth. Today on Earth all the spirits of these aliens have attached themselves to our bodies and are the root cause of the false reality that all but Scientology?s ?Homo Novis? or OT 8?s on earth experience.
According L. Ron Hubbard, the dictator of the "Galactic Confederacy" who, 75 million years ago, brought billions of his people to Earth in a DC-8-like spacecraft, stacked them around volcanoes and killed them using hydrogen bombs. Official Scientology dogma holds that the essences of these many people remained, and that they form around people in modern times, causing them spiritual harm. Members of the Church of Scientology widely deny or try to hide the Xenu story.
These events are known within Scientology as "Incident II", and the traumatic memories associated with them as The Wall of Fire or the R6 implant. The story of Xenu is part of Scientologist teachings about extraterrestrial civilizations and alien interventions in Earthly events, collectively described as space opera by Hubbard. Hubbard detailed the story in Operating Thetan level III (OT III) in 1967, warning that the R6 "implant" (past trauma) was "calculated to kill (by pneumonia etc) anyone who attempts to solve it".
The Xenu story is part of the Church of Scientology's secret "Advanced Technology",normally only revealed to members who have already contributed large amounts of money. The church avoids mention of Xenu in public statements and has gone to considerable effort to maintain the story's confidentiality, including legal action on the grounds of both copyright and trade secrecy. Despite this, much material on Xenu has leaked to the public via court documents, copies of Hubbard's notes, and the Internet.