Psychoanalysis
Psychoanalysis is a means of understanding human thought and emotions, as well as potentially treating malfunctions, originating with the work of Sigmund Freud. A neurologist by training, he saw symptomatology that could not be explained by the neurobiology of the time. Part of the reason psychoanalysis is sometimes considered prescientific, or even pseudoscience, is the much greater modern understanding of neurosciences. Nevertheless, he did examine how what he termed conscious and unconscious thinking could affect a patient's world view.
A broader view today bases psychodynamic psychotherapy on principles derived from psychoanalysis.
Theory
Freud began a private practice in Vienna in 1886 through 1896, in which he abstracted concepts from his observations of his patients.
Major students
Several of his close associates, including Alfred Adler, Carl Jung and Otto Rank eventually broke away to develop their own styles of psychotherapy. Others, such as Karen Horney, stayed with a Freudian approach but developed it further.