The term psychoanalytical theory usually refers to a theory that explains the psychological functioning and behavior of humans. Psychoanalysts, in addition, also distinguish the theory of techniques, which describes how a psychoanalyst conducts treatment and explains why certain interventions in certain situations produce effects on the client in therapy.
Psychoanalytical theory is constantly evolving as a result of the work with clients in therapy. Particularly difficult clients represent a challenge for understanding and hence help reaching new discoveries about the functioning of psyche. Freud was constantly changing and expanding his theories. This trend also continued after Freud. Today, new theoretical models developed by some psychoanalysts are indispensable for the understanding of contemporary psychic disorders. Among the better known ones are Melanie Klein, Donald Winnicott, Heinz Kohut, Otto Kernberg, Wilfred Bion, André Green, Antonino Ferro, and many others.