A version of this article first published in 2012.

(CNN) Chances are -- unless you live in Los Angeles -- the only time you hear about Scientology is when it's connected with a Hollywood celebrity.

Yet there's a lot more to this religion than just its ties to Tinseltown. Scientology is probably one of the most successful new American faiths to have emerged in the past century. But despite its success -- and like a lot of other belief systems -- what Scientologists believe and how they perceive a higher power is often misunderstood.

Religious scholar Reza Aslan explores the origin and central ideas of this faith on his CNN show, "Believer."

Dear Scientology critics: diff btwn Xenu dropping Aliens on earth, and God creating man out of dirt is that one story is older than other.

Here's a look at the basics about Scientology:

What is Scientology?

Scientology describes itself as a religion that was founded in the 1950s by L. Ron Hubbard.

At the core of Scientology is a belief that each human has a reactive mind that responds to life's traumas, clouding the analytic mind and keeping us from experiencing reality. Members of the religion submit to a process called auditing to find the sources of this trauma, reliving those experiences in an attempt to neutralize them and reassert the primacy of the analytic mind, working toward a spiritual state called "clear."

The process involves a device called E-meter, which Scientologists say measures the body's electric flow as an auditor asks a series of questions they say reveals sources of trauma.

"Auditing uses processes - exact sets of questions asked or directions given by an auditor to help a person locate areas of spiritual distress, find out things about himself and improve his condition," according to the Church of Scientology's website.

The church goes on to say, "Science is something one does, not something one believes in."

Auditing purports to identify spiritual distress from a person's current life and from past lives. Scientologists believe each person is an immortal being, a force that believers call a thetan.

"You move up the bridge to freedom by working toward being an 'Operating Thetan,' which at the highest level transcends material law," says David Bromley, a professor of religious studies at Virginia Commonwealth University. "You occasionally come across people in Scientology who say they can change the material world with their mind."

Bromley and other scholars say the church promotes the idea of an ancient intergalactic civilization in which millions of beings were destroyed and became what are known as "body thetans," which continue to latch onto humans and cause more trauma.

Advanced Scientologists confront body thetans through more auditing.

Bromley says the church discloses that cosmic history only to more advanced Scientologists. The church's media affairs department did not respond to requests for comment to this story.

In a 2008 CNN interview, church spokesman Tommy Davis was asked whether the basic tenet of the Church of Scientology was to rid the body of space alien parasites.

"Does that sound silly to you?" laughed Davis. "I mean, it's unrecognizable to me. ... People should really come to the church and find out for themselves what it is."

Who was L. Ron Hubbard?

L. Ron Hubbard was the founder of Scientology. Born in Nebraska in 1911, Hubbard was the son of a U.S. Navy officer who circled the globe with his family, according to Scientology expert J. Gordon Melton, a fellow at Baylor University's Institute for Studies in Religion who writes about Scientology on the religion website Patheos.

Hubbard attended the George Washington University in Washington, D.C., but left before graduating to launch a career as a fiction writer, gravitating toward science fiction.

Photos: L. Ron Hubbard and the Church of Scientology Photos: L. Ron Hubbard and the Church of Scientology After serving in World War II, writer L. Ron Hubbard published a series of articles and then a book on what he described as a new approach to mental health. "Dianetics: The Modern Science of Mental Health" was first published in 1950, and it quickly became a best-seller. In 1954, Hubbard founded the Church of Scientology. Hide Caption 1 of 16 Photos: L. Ron Hubbard and the Church of Scientology Hubbard and his children in December 1959. They are testing a device called an E-meter, which Scientologists say measures the body's electric flow as an auditor asks a series of questions that they say reveals sources of trauma. At the core of Scientology is a belief that each human has a reactive mind that responds to life's traumas, clouding the analytic mind and keeping us from experiencing reality. Hide Caption 2 of 16 Photos: L. Ron Hubbard and the Church of Scientology Hubbard works in his greenhouse in December 1959. Hide Caption 3 of 16 Photos: L. Ron Hubbard and the Church of Scientology Hubbard in the south of France in May 1968. Hide Caption 4 of 16 Photos: L. Ron Hubbard and the Church of Scientology Hubbard talks with reporters in his office in 1974. Many groups and individuals have challenged Scientology's legitimacy as a religion. Scientologists have faced opposition from the medical community over the religion's claims about mental health, from the scientific community over its claims about its E-meters and from other religious groups about its status as a religion. Hide Caption 5 of 16 Photos: L. Ron Hubbard and the Church of Scientology Hubbard poses for a portrait in New York in January 1982. He died in 1986. Hide Caption 6 of 16 Photos: L. Ron Hubbard and the Church of Scientology The entrance to the Los Angeles headquarters of the church in March 1998. Hide Caption 7 of 16 Photos: L. Ron Hubbard and the Church of Scientology Confetti rains down as actor Tom Cruise, left, embraces David Miscavige, the leader of the Church of Scientology, at the opening of a new church in Madrid in September 2004. Cruise is one of the world's most prominent Scientologists. "What I believe in my own life is that it's a search for how I can do things better, whether it's being a better man or a better father or finding ways for myself to improve," Cruise told Playboy magazine. "Individuals have to decide what is true and real for them." Hide Caption 8 of 16 Photos: L. Ron Hubbard and the Church of Scientology Miscavige speaks during the inauguration of the Madrid church in September 2004. Hide Caption 9 of 16 Photos: L. Ron Hubbard and the Church of Scientology Scientology made headlines in June 2005 when Cruise got into a heated debate with "Today" host Matt Lauer over psychiatric drugs. The Church of Scientology's website says that "the effects of medical and psychiatric drugs, whether painkillers, tranquilizers or 'antidepressants,' are as disastrous" as illicit drugs. Hide Caption 10 of 16 Photos: L. Ron Hubbard and the Church of Scientology Actress Kirstie Alley and actor Tait Ruppert perform during the Church of Scientology's Christmas Stories XIV benefit in December 2006. Hide Caption 11 of 16 Photos: L. Ron Hubbard and the Church of Scientology A volunteer from the Church of Scientology touches an injured woman in Port-au-Prince, Haiti, after the devastating earthquake there in January 2010. Hide Caption 12 of 16 Photos: L. Ron Hubbard and the Church of Scientology An E-meter sits next to Hubbard's book "Self Analysis" in Zurich, Swizerland, in January 2011. Hide Caption 13 of 16 Photos: L. Ron Hubbard and the Church of Scientology Actor John Travolta and his wife, actress Kelly Preston, attend the opening of a Scientology Mission in Ocala, Florida, in May 2011. Hide Caption 14 of 16 Photos: L. Ron Hubbard and the Church of Scientology A headquarters for the Church of Scientology is seen in Clearwater, Florida, in January 2013. Hide Caption 15 of 16 Photos: L. Ron Hubbard and the Church of Scientology In November 2013, Miscavige dedicates the massive Clearwater building as the church's new spiritual headquarters. Hide Caption 16 of 16

After serving in World War II, Hubbard published a series of articles and then a book on a what he described as a new approach to mental health, which he called Dianetics. His book by the same name quickly became a best-seller.

The success provoked Hubbard to establish a foundation that began to train people in his auditing techniques. In 1954, the first Church of Scientology opened in Los Angeles, with other churches opening soon after. Hubbard died in 1986. The church is now led by David Miscavige.

Why is the church so controversial?

Many groups and individuals have challenged Scientology's legitimacy as a religion.

Scientologists have faced opposition from the medical community over the religion's claims about mental health, from the scientific community over its claims about its E-meters and from other religious groups about its status as a religion.

"It's part therapy, part religion, part UFO group," says Bromley. "It's a mix of things that's unlike any other religious group out there."

For a long time, the Internal Revenue Service denied the Scientologists' attempts to be declared a church with tax-exempt status. But the IRS granted them that status in 1993.

Many members say the church is largely about self-improvement.

"What I believe in my own life is that it's a search for how I can do things better, whether it's being a better man or a better father or finding ways for myself to improve," Tom Cruise told Playboy magazine . "Individuals have to decide what is true and real for them."

What does Scientology teach about psychiatry?

L. Ron Hubbard rejected psychiatry and psychiatric drugs because he said they interfered with the functioning of the rational mind. Scientologists continue to promote that idea.

The Church of Scientology's website says that "the effects of medical and psychiatric drugs, whether painkillers, tranquilizers or 'antidepressants,' are as disastrous" as illicit drugs.

How many Scientologists are there?

That's a matter of considerable dispute.

Photos: Celebrity Scientologists Photos: Celebrity Scientologists Actor John Travolta became a Scientologist in 1975 and has been one of the faith's strongest supporters. Hide Caption 1 of 17 Photos: Celebrity Scientologists Tom Cruise's 2012 split with Katie Holmes triggered lots of questions about any role that Cruise's status as a Scientologist played in the divorce. The church issued this statement about the issue. Hide Caption 2 of 17 Photos: Celebrity Scientologists In 2010, actress Kirstie Alley told CNN's Larry King that Scientology, her faith for three decades, helped her lose weight. Hide Caption 3 of 17 Photos: Celebrity Scientologists Former Fox News host Greta Van Susteren (now with MSNBC) joined Scientology after marrying her Scientologist husband, attorney John Coale, in the 1980s. Hide Caption 4 of 17 Photos: Celebrity Scientologists Nancy Cartwright, a high-profile member of the Church of Scientology, is also the voice of Bart Simpson on the animated series "The Simpsons." Hide Caption 5 of 17 Photos: Celebrity Scientologists Actress Jenna Elfman is best known for her starring role in the TV sitcom "Dharma and Greg." Hide Caption 6 of 17 Photos: Celebrity Scientologists Actress Juliette Lewis defended Scientology and fellow proponent Tom Cruise after his 2012 divorce. Hide Caption 7 of 17 Photos: Celebrity Scientologists Beck came into the spotlight in the '90s with his breakthrough single, "Loser." Hide Caption 8 of 17 Photos: Celebrity Scientologists Actress Anne Archer was nominated for an Academy Award for her role in the 1987 movie "Fatal Attraction." Hide Caption 9 of 17 Photos: Celebrity Scientologists Catherine Bell starred in the TV series "JAG" and "Army Wives." Hide Caption 10 of 17 Photos: Celebrity Scientologists Actor Danny Masterson is known for his role in "That '70s Show." Hide Caption 11 of 17 Photos: Celebrity Scientologists Actress and model Bijou Phillips wed Masterson in 2011. Hide Caption 12 of 17 Photos: Celebrity Scientologists Former "Glee" and "Party of Five" actress Jennifer Aspen credits Scientology with saving her life and for her successful career Hide Caption 13 of 17 Photos: Celebrity Scientologists When asked about his Scientology faith, actor Giovanni Ribisi said, "It's a personal thing, it's something that works for me, and I think it's that simple." Hide Caption 14 of 17 Photos: Celebrity Scientologists Actress Lynsey Bartilson co-starred in the sitcom "Grounded for Life." Hide Caption 15 of 17 Photos: Celebrity Scientologists Actress Erika Christensen played Julia on the critically acclaimed television series "Parenthood." Hide Caption 16 of 17 Photos: Celebrity Scientologists Veteran rapper Doug E. Fresh has performed at Church of Scientology events. Hide Caption 17 of 17

The Church of Scientology says it has 10,000 churches, missions and groups operating in 167 countries, with 4.4 million more people signing up every year.

Scholars say that, despite the global proliferation of church buildings, the membership numbers are much lower than the church claims, likely in the hundreds of thousands. Several of the church's followers are Hollywood celebrities.