What is lineage?
In Tibetan Buddhism, lineage is essential. Lineage indicates that teachings and the teacher transmitting them have an unbroken line all the way back to Buddha Shakyamuni, ensuring that the knowledge is true and unfabricated. Experiential knowledge is passed from master to student through oral instruction which indicates that it is not just theory, it is embodied wisdom of enlightened beings, therefore becoming a source of trust.
Kagyu is one of the main schools of Tibetan Buddhism Vajrayana.
“Ka” = enlightened instructions and teachings
"Gyu” = continuity or the uninterrupted lineage of masters and students
Therefore Kagyu refers to “the uninterrupted teachings of enlightenment” and is thus called the “Lineage of oral instruction”