During a long time in the history, Tibetan kings reigned with a combination of religion and politics. Most Tibetan people believe in Buddhism and they are devout to it. It has a strong mysterious color, especially with the reincarnation system which is a distinct feature of Tibetan Buddhism. Tibetan Buddhism focuses on religious practice and has a large number of followers. Numerous Buddhist Acts emerged after the mid-11th century, including the Nyingma, Gatang, Sagya, Gagyu, Zhigyed, Gyoyul, Gyonang, Kodrag and Xalhu sects. The latter five were rather weak owing to the lack of political support. They were thus forced to join force or were otherwise annexed by other sects, and as individual entities fell into the oblivion of the long flow of history. The following five sects enjoyed impressive popularity:

1. Nyingmapa, the Ancient Ones, dates from around 750 with Padmambhava. Its name means "old", since it was the oldest of the Buddhist sects in Tibet. The Nyingmapa lamas wear red robes and hats, so it is also known as the Red Sect. It has a loose organization and focuses on mantra practice. Its lamas may marry and usually live in small groups. The sect retains many more of the Bon features than the other sects. Nyingmapa lamas believe that the mind is pure and that by cultivating one's being in such a way as to reject all outside influences, it is possible to become as one with Buddha. This sect has a greater number of deities than the other four. The major Nyingmapa monasteries are the Mindroling Monastery and the Dorje Drak Monastery. The former is particularly important for its collection of Tibetan calligraphy.

2. Kahdampa ordains that Buddha's acts and teachings should be the doctrines of cultivation. It is based on the teachings of Atisha, who arrived from India in 1042. The tradition lays stress on scriptures and discipline and emphasizes Tantra can be imparted to only to a select few. Kahdampa preaches samsara and retribution, so it underwent rapid development. By comparison with the other sects, its Yoga and Tantra remain pure. The main monastery is the Nechung Monastery, the hegumen (or abbots) of which acted as regents during the ethnic group of the Dalai Lamas and conducting the government of Tibet. Later this sect converted to Gelugpa.

3. Kagyupa was originated by two great teachers, Marpa and Milarepa. Kagyupa means "to teach orally" and its focus is on Tantric teaching. Since Marpa and Milarepa wore white robes, this sect is also called White sect. Its doctrines are unique and stresses a combination of the practice of quasi-qigong and Buddhist satori. It also advocates asceticism and obedience as the source of enlightenment. An important contribution of Kagyupa was the creation of tulku (reincarnating lamas) system, in which an existing lama can show evidence of his prior incarnations. Kagyupa's principal shrine is the Tsurphu Monastery, the traditional seat of Karmapa lama.

4. Sakyapa dates from 1073 and was founded at the Sakya Monastery after which it was named. Later, the sect was to govern Tibet for a period. As the monastery wall was painted with red, white and black stripes, the order became known colloquially as the Colorful Sect. Sakyapa's doctrines persuade people to do good deeds so that they may gain a good incarnation in their next samsara and to discard all temporal desires to ensure relief from pain.

5. Gelugpa is the order of Dalai Lama and Panchen Lama and is also called the Yellow Sect since they wear yellow hats. It was founded by Tsong Khapa, a great Buddhist reformer, in 1407. It absorbed Kahdampa and carried on Atisha's tradition. It stresses strict discipline and study of the scriptures. Its successful reform made it dominant in Tibet after the 17th century, leaving other sects to play a minor role. Its six main monasteries are the Ganden Monastery, Ta'er Monastery, Drepung Monastery, Labrang Monastery, Sera Monastery and Tashilhunpo Monastery.