Direct introduction or direct transmission - introduction of the student's mind to the nature of mind. As a result, the mind is not thinking, judging or creating anything and one can discover the state of instant presence, or rigpa.
Direct introduction deals with the three experiences of emptiness, clarity and sensation of pleasure. These three experiences correspond to the Mind, Voice and Body, respectively. The teacher explains how to produce these experiences, and then, on the basis of these experiences, one works with the teacher to discover one's state.
It is important to understand that real nature cannot be shown nor taught. It has to be discovered and the role of the teacher is to help one understand this.