Change your preferences here.
Deals damage. The target's Defense stat, and not its Special Defense, is used in damage calculation. All other factors work as expected.
Psyshock is primarily used on Psychic-types as a way to hit opponents with a "physical" attack, allowing them to muscle through special walls. The power drop compared to Psychic makes the latter preferred in many situations. However, Psyshock is better for Calm Mind wars.
Psychic is an option with a higher Base Power that does not target the foe's Defense.
Psystrike is a move with the same effect but 100 Base Power; however, it is limited in distribution to only Mewtwo, which limits its widespread use.