Personality refers to characteristic patterns of thinking, feeling and behaving. It arises from both innate factors like genetics as well as environmental influences. Major theories of personality include Freud's psychodynamic theory, the Big Five trait theory, and Jung's theory of the collective unconscious. Personality can be assessed through objective standardized tests that measure traits or through projective tests that analyze responses to ambiguous stimuli. Understanding personality has practical applications and improves quality of life by providing insights into human behavior and potential for growth.