Before Buddhism was brought to Tibet, the Tibetans had their believes in "Bon". "Bon" is a kind of folk beliefs which gives offerings to ghosts and gods and receives their blessing. It belongs to local folk beliefs.
In the Chinese Tang Dynasty, the Tibetan King Songtsän Gampo brought “Buddhism” to the Tibetan people which became the state religion. The so-called “Buddhism” is Tantric Buddhism which spreads out during the final period of Indian Buddhism. The Tantric Buddhism is also named "left hand tantra" because of its tantric sexual practices. In order to suit Tibetan manners and customs, the tantric Buddhism was mixed with "Bon". Due to its beliefs of ghosts and sexual practices, it became more excessive.
The tantric Master Atiśa spread out the tantric sex teachings in private. Padmasambhava taught it in public, so that the Tibetan Buddhism stands not only apart from Buddhist teachings, but also from Buddhist form. Thus, the Tibetan Buddhism does not belong to Buddhism, and has to be renamed "Lamaism".