(USA TODAY) -- The Church of Scientology has long been controversial.
"Few other groups have been investigated and accused of wrongdoing at various times by so many government agencies (including the Internal Revenue Service, the Food and Drug Administration and the Federal Bureau of Investigation)," according to the World Religions & Spirituality Project at Virginia Commonwealth University, an online encyclopedia of religions.
Scientology is decried as a cult by conservative evangelicals. It's also been the subject of major investigations by media organizations including the Tampa Bay Times, New York Times and New Yorker.
But Scientology is most often in the headlines when its celebrity followers make news. Katie Holmes has said nothing publicly about Tom Cruise's allegiance to the faith or whether it's a factor in her seeking a divorce and full custody of their daughter, Suri. Yet, the celebrity breakup raises interest in the religion and its teachings.
Here's a quick primer, based on the Scientology.org website and interviews with J. Gordon Melton, professor of American Religious History at Baylor University, and David Bromley, professor of religious studies and sociology at Virginia Commonwealth. Scientology's press office did not return calls.
What is Scientology?
The religion, founded by the late author L. Ron Hubbard in 1954, is about finding self-knowledge. The focus is on "becoming your authentic self to reflect your true spiritual essence," says Bromley.
Scientology parallels many major Western religions in making a claim that it is the single best way to find truth. But it is more like Buddhism or Hinduism in that it does not rely on the Bible, God or Christ. Says Melton, "The basic idea is that you get yourself in order in this world and work toward an understanding of the larger world."
There is no holy scripture, although Scientologists rely on the insights in nearly two dozen books by Hubbard, primarily his the best-selling book on a rational approach to mental health, Dianetics.
According to Scientology.org, human beings are neither body nor mind, but immortal spiritual beings with unlimited capabilities, "even if not presently realized."
Unlike the Christian belief that mankind is born into sin, Scientology teaches that "Man" is "basically good, and his spiritual salvation depends upon himself and his fellows and his attainment of brotherhood with the universe."
That is accomplished through classes and a technologically based personality assessment called "auditing," designed to help each person overcome the effects of traumatic experiences in their lives, says Bromley.
Critics object to Scientology's goals that dismiss Christian and Jewish concepts of God, morality and the afterlife, as well as its secretive methods and ban on use of psychiatry and psychiatric drugs.
The church battled for years in court to secure IRS recognition as a tax-exempt religion in 1993.
How big is the Church?
The official website says 10,000 churches, missions and groups in 167 countries. There is no independent checks on the number of adherents claimed by any major religious group.
The 2001 American Religious Identification Survey found 55,000 self-identified Scientologists in the USA. Melton estimates there are about 100,000 adherents today, with about 10% clustered in the St. Petersburg, Fla., vicinity, near the Church's world headquarters.
What are Scientology's rules on marriage, divorce and remarriage?
Scientology.org describes a marriage ceremony, including an example written by Hubbard, as a serious vow of love, shared visions of reality and commitment to communicate with each other.
Most Western religions have very specific rules and procedures for marriage or divorce. Scientology does not, and Hubbard himself was divorced.
The exception is for the highest level of the church administrators, known as Sea Org, which functions similar to a monastic order in Christianity and has strict conduct rules on marriage and divorce, says Bromley. To his knowledge, there are no celebrity Hollywood names in Sea Org.
Neither are there rules for remarriage, as in Catholicism and Orthodox Judaism. Nicole Kidman, who married and later divorced Cruise, had their marriage annulled by the Catholic Church as spiritually invalid.
What does Scientology say about rearing children?
Very little, says Melton. There are not many children - yet. Because Scientology is a new religion, its members are chiefly adult converts.
Unlike an ethnic religion such as Judaism, a child of a Scientologist parent, such as Cruise's daughter, is not born into the religion, Melton says.
"There are some Scientology parochial schools, called Delphi Academies, where they apply Hubbard's educational ideas, but they are not all that different than other religions that teach their values to children in their private schools," says Melton.
Melton points out that people call it "indoctrination" when they disagree with what is taught: "You 'teach' your children; other people 'indoctrinate' their children."