The conception that Freud believed all motivation was sexual has a lot to do with the fact that he expanded sexuality to include all forms of physical pleasure. However, he did actually believe that a search for pleasure was the whole of human motivation—he also provided an explanation for such things as suicide, self-mutilation, etc. Freud identified two instincts that rule human action—Eros (life instinct) and Thanatos (death instinct). However, although not all Freud’s theories had to do with the more commonly accepted definition of sexuality, a large number of them did.
For example, Freud’s “Infantile Sexuality” theory details the psychological stages of sexual development in children under the age of five. Freud argues that infants gain pleasure through the act of sucking (the oral stage) and toddlers through defecating (the anal stage). It is at the phallic stage that an Oedipus complex is actually supposed to develop, though that complex (in a healthy child) submerges around the age of five. Freud’s theory of the Oedipus complex actually comes from an examination of his own childhood with the fantasy that his half-brother was actually his father. He believed that fantasy was due to jealousy of the affection his mother gave to his father. Freud believed hysteria, obsessive hygiene, homosexuality, etc. could be traced back to failure to cope at one of the stages of infantile sexuality.
Freud’s theory on the adult mind was that it was composed of three parts: id, ego, and superego. The id is the part of the mind responsible for sexual desires, etc.; the superego is the source of conscience (which Freud defines as socially imposed control mechanisms), and the ego is the conscious self created by the tensions between id and superego. One of Freud’s key concepts was the mind’s self-defense mechanisms which dealt with socially unacceptable urges. Some of these were repression (pushing conflicts back into the unconscious), sublimation (channeling the sexual drives into the achievement socially acceptable goals, in art, science, poetry, etc.), fixation (the failure to progress beyond one of the developmental stages), and regression (a return to the behaviour characteristic of one of the stages).
Finally, Freud’s concept of psychoanalysis as therapy basically instructed the psychologist to get to know his patient, taking note of all unconscious actions, and determining through those what had gone wrong in the wiring between id, ego, and superego. Basically, Freud believed a psychologist could understand what was going on in a patient’s subconscious that the patient refused to admit and, by knowing the patient’s mind better than the patient himself, help solve the problem by telling the patient what the patient actually is thinking so the patient must deal with it directly rather than allowing it to be expressed in unhealthy ways.