A wish is a mental impulse or desire to obtain satisfaction.
In Studies on Hysteria Freud employed the term wish to designate a forbidden desire, speaking,
Freud placed increasing emphasis on a more precise definition of the wish, which became highly influential in the development of psychoanalytic theory.
the wish was produced by unconscious mnemonic traces that were fixed indelibly by the earliest experiences of infantile satisfaction.
The aim of the wish is to recreate that experience, following paths laid down by primary process thought, taking into account the "logic" of unconscious drives to bypass censorship.
The wish accomplishes this by being articulated in the language of the most profoundly cathected ideas.
This is what led Freud to define the dream as hallucinatory wish-fulfillment.