One of the most popular personality theorists is Sigmund Freud, and he propounded the Theory of Personality.
This refers to the study of how the personality of a person develops and can be useful in studying personality disorders.
Sigmund Freud was a psychologist and psychoanalyst that was responsible for the Theory of Personality where he talked about the Id, Ego, and Superego in a person's personality.
Please note that your question is incomplete so I gave you a general overview to help you get a better understanding of the concept.
Read more about Sigmund Freud here:
https://brainly.com/question/2706543