The four main personality theories are the psychoanalytic, the trait, the humanistic, and the social-cognitive theories.
Psychoanalytic theory: the most popular theory of personality is that of psychoanalysis, which was mainly introduced by Sigmund Freud. This theory focuses on the unconscious and the subconscious mind; it suggests that human behavior is shaped by past experiences and one's reactions to those experiences, which never leave the mind.
Freud argues that personality is made out of three key components: the id, ego and super-ego; the id represents the needs and desires, the super-ego represents the moral ideas and standards that people have, and the ego allows people to control their urges and desires and satisfy them in ways that are reasonable and socially acceptable.
Trait theory: the trait theory is based on traits as specific characteristics of one's personality or as characteristics that can determine a person's behavior. Psychologist Gordon Allport identified three main types of traits: cardinal traits (dominant and deterministic traits, such as being narcissistic), central traits (meaningful attributes, such as being kind, smart, mean) and secondary traits (which appear occasionally in specific situations—for example, being nervous before taking tests). Psychologist Hans Eysenck, on the other hand, identified three main traits: introversion/extroversion, neuroticism/stability, and psychoticism/ socialization.
Humanistic theory: the humanistic theoretical approach to the study of personality focuses on the individual as a whole and is optimistic in nature, as it focuses on the people's ability to reach their full potential and become the best versions of themselves.
Social cognitive theory is based upon two key principles: (a) that the psychological person, the environment, and behavior reciprocally influence one another; and (b) that people are best understood in terms of conscious cognitive capabilities that enable them to symbolically represent events, to reflect upon themselves, and to act as agents of their own development (Bandura, 1986, Bandura, 1997; Cervone & Williams, 1992).