Prajna is the transcendent wisdom of the emptiness, the Absolute or Void, which the Bohisattva enters through the previous Paramitas.  The fulfillment and expression of Generosity, Ethics, Patience, Action and Meditation, the direct experiential knowledge by which the spiritual aspirant can overcome and understand suffering.  Lecture relates to the Sephirah Chesed, the world of Prajna or inner wisdom. Lecture quote:

"By Prajna we do not mean the simple insight or simple wisdom that our intellect generally conceives, or attributes to that term "wisdom." We think of wisdom as something that an old person gathers or has, a wise old person, having gained wisdom through experience. This is not the kind of wisdom that we are describing. This kind of wisdom has nothing to do with age, it has nothing to do with time. It cannot be acquired; it cannot, because it exists already. We are starting to enter into something very profound. In order to understand Prajna, we have to move beyond the realm of the intellect"