The Church of Scientology maintains a wide variety of beliefs and practices. The core belief holds that a human is an immortal, spiritual being (thetan) that is resident in a physical body. The thetan has had innumerable past lives, some of which, preceding the thetan's arrival on Earth, were lived in extraterrestrial cultures. Based on case studies at advanced levels, it is predicted that any Scientologist undergoing auditing will eventually come across and recount a common series of past-life events.

Scientology describes itself as the study and handling of the spirit in relationship to itself, others, and all of life. Scientologists also believe that people have innate, yet suppressed, power and ability which can be regained if cleared of unwanted behavioural patterns and discomforts. Scientology is described as "a religion to help people use scientific approaches to self-actualize their full potential." Believers reach their full potential "when they understand themselves in their true relationship to the physical universe and the Supreme Being. " There have been many scholarly studies of Scientology and the books are freely available in bookshops, churches and most libraries.

The Church of Scientology believes that "Man is basically good, that he is seeking to survive, (and) that his survival depends on himself and his attainment of brotherhood with the universe," as stated in the Creed of the Church of Scientology.

Roy Wallis of Columbia University describes Scientology as "a movement that straddles the boundaries between psychology and religion, [offering] a graded hierarchy of 'auditing' and training" with the intention of releasing the individual's full potential.

Scientology does not require that their members must exclusively believe in Scientology, distinguishing it from biblical religions. Scientologists may profess belief in other religions, such as Protestantism and Catholicism, and may participate in their activities and sacred rites. Jacob Neusner emphasizes this in the section on Scientology in his book World Religions in America. According to J. Gordon Melton, "Scientologists aim to utterly remake the world instead of taking refuge from it," as they participate in culture instead of being isolated. Scientology is inherently nondenominational and open to individuals, regardless of religious background; according to Mary A. Mann, it contains the elements necessary for a global religion and caters to people of all different ethnicities and educational upbringing.