There are four major schools of Tibetan Buddhism. The Practicing Lineage or the Kagyu Lineage is one of the middle schools, which came after the old, or ancient, schools. The Kagyu lineage developed through various Tibetan masters and scholars who visited India and received teachings there and then returned to establish their particular situation in Tibet. Namely, there was the famous translator-saint Marpa, who visited India three times and brought the teachings he received there to Tibet. His disciple Milarepa was the greatest yogic poet of Tibet, or shall we say, singer-poet. We could call him the first Tibetan blues singer. And then there was his disciple Gampopa, and then Gampopa's descendants established the lineage of the Karmapas. At this point, the lineage of the Kagyu, the Practicing Lineage, consists of something like forty-five generations-up to the time of the Eleventh Trungpa, whoever he might be! (Chögyam Trungpa was the Eleventh Trungpa.)
From "The Practicing Lineage," in The Mishap Lineage: Transforming Confusion into Wisdom.