Short background history of Buddhism in Tibet.

The Buddha Sakyamuni was born in Lumbini, Nepal as prince Siddhartha
in 563 B.C. and lived to be 80 years old. As a young man, Siddhartha
left the pleasures of royal life in search of an end to the miseries
of existence. After quickly perfecting the meditation practices
taught by the most advanced teachers of his time, Siddhartha
realized that enligthenment could not be attained by extreme methods
of asceticism or by achievement of concentration states. By
practicing the middle way of gently examining the nature of his own
mind he attained Buddhahood, the enligtened stage.
The historical Buddha Sakyamuni, gave many
different kinds of teachings in order to accommodate the different
capacities of beings.
All these teachings can be divided into two
catagories of the Sutrayana and the Tantrayana. Although the Buddha
gave oral teachings, his early disciples recorded his instructions
in writing and thus passed them on in this original form. Buddhist
masters also authored many treatises that explain the Buddha's
teachings. The emphasis was on the authentic and accurate
transmission of the teachings, as this is of prime importance.
Throughout the centuries, as disciples became teachers in their turn,
different lines of transmission came about, each with their own
characteristics.
Buddhism in Tibet includes all the teachings that originated in
India. Through the effort of Tibetan translators and Indian masters
the whole corpus of the Buddhist teachings was translated into
Tibetan. With this foundation, Buddhism flourished in Tibet until
the middle of the 20th century.
In the 8th century the Tibetan king,
Trisong Detsen, invited two Buddhist masters, Guru Rinpoche and
Shantarakshita, to Tibet. At the same time the king had important
Buddhist texts translated into Tibetan. This early activity of
teaching and translation gave rise to the Nyingma tradition, the
"Old Tradition". The teachings in the Nyingma tradition
are based on the texts of this early period of translation.
Durung the 11th century there was a second period of translation
which involved the revision of earlier terminology as well as new
translations. The traditions that base their transmission on that
period are referred to as the Sarma traditions, the "New
traditions".
Of these, the Kagyu, Sakya and Gelug are the best
known.
The Kagyu tradition was introduced to Tibet by Marpa the translator,
who emphasized four special transmissions that trace their origin to
the Indian siddha Tilopa and other Indian masters of the Mahamudra
lineage.
The Sakya tradition was founded by Khon Konchog Gyalpo who focused
his transmission on the teachings expounded by the Indian Mahasiddha
Virupa.
The Gelug tradition was established by Tsongkhapa who stressed the
teachings of the Kadampa school founded in Tibet by the Indian
master Atisha.