Sigmund Freud developed a comprehensive theory of personality comprising three interacting parts: the id, ego, and superego. The id operates according to the pleasure principle, seeking immediate gratification. The ego develops to cope with reality. The superego incorporates social standards of right and wrong through ego ideals and conscience. Freud's psychodynamic theory provides a framework to understand human behavior and development through examining early relationships, defense mechanisms, and resolving psychosexual stages from oral to genital.