Kagyu Sect

Kagyu sect of Tibetan Buddhism is also known as Oral Lineage. The tradition is one of the four main schools of Tibetan Buddhism along with Nyingma, Skaya, and Gelug. The lineage is often called the practice lineage. The tradition places great importance to Intensive meditation practise of Guru Yoga, The Power of devotion and transmission from the master to disciple. Mahamudra “The Great Seal” in the prime teaching of the Kagyu. 

https://itibettravel.com/tibet/tibetan-religion/tibetan-buddhism-2/kagyu-sect-of-tibetan-buddhism/