When talking about the Guru, we must distinguish between the external form and the Guru in our heart: "The illustrative guru, who is the external form of the guru, illustrates through his teachings the actual guru, which is the luminosity within your own heart. The guru's instructions awaken the ultimate guru within." In this statement, the outer guru called "the illustrative guru," the one who has realized the nature of mind (Buddha nature) and shows this nature to you so that you can then realize the nature of mind. The outer guru is called the illustrative guru because he gives us the indication that leads us to realize the ultimate guru. When this happens, you will realize the bond between your mind and the mind of the guru. It is like the string of a mala. You will realize the nature of your own mind and the nature of the guru's mind to be the same by nature, an inseparable union. When this awareness occurs, you will see your own true nature, which is when you see the ultimate guru being your Buddha nature. But because we do not recognize it, we just ignore our true nature. That is why we rely on the master, on the outer guru, the rupakaya "master who appears in an ordinary form with a face and hands”. The illustrative guru manifests to us in order to help us realize the ultimate guru, which is the clear light in the center of our hearts. Once this is awakened through the teacher's instructions, it is precisely this that we put into practice: the ultimate teacher beyond any arising. - Garchen Rinpoche