The Tragic Myth, according to Nietzsche in The Birth of Tragedy, is a symbolic or imagistic representation of Silenus' (or Dionysian) wisdom. The Dionysian manifests himself through Apollonian processes of knowledge and representation (see explanation of Nietzsche's Dionysian and Apollonian). The phenomenal world denies itself in this representation that it exhibits without conceptualizing the original background of existence. In other words, tragic theatre is where the relationship between wild Dionysus and bright Apollo take place.
Tragic signification takes place here, according to Nietzsche, without conceptual mediation. It is no longer the plot that is the fulcrum in question, but above all a transmission such that it snatches the individual and his limits, dissolving him into the whole experience of the act.