Final answer:
Freud's theory of psychosexual development posits that human personality evolves through distinct stages, each characterized by a focus on a specific erogenous zone.
Step-by-step explanation:
Freud's theory begins with the oral stage, where an infant's pleasure centers on oral activities such as sucking and biting. This stage is crucial in shaping one's dependency and trust issues later in life. In the phallic stage, children become aware of their bodies and the differences between males and females. The Oedipus and Electra complexes emerge, influencing the development of gender identity and moral values.