Physical courage is performing an action in spite of the fear of physical pain or death. Intellectual courage is overcoming the fear of complication and the natural aversion to feelings of confusion and bewilderment. Moral courage is always doing what you feel to be right regardless of the potential negative personal consequences.
It is possible to possess physical courage and be neither intellectually or morally brave. It is possible to be intellectually courageous and have no physical or moral courage. It is, however, impossible to be morally courageous and not possess the other two. Therefore, moral courage is the most potent of the three.