Tibetan Buddhism

Tibetan Buddhism derives in the confluence of Buddhism and yoga which began to arrive in Tibet from India briefly round the late eighth century after which more steadily in the thirteenth century onwards. Indian Buddhism around that point had incorporated both Hindu yogic and tantric practices combined with the classical teachings from the historical Buddha who lived around 500 BC. It acknowledged there were two paths to enlightenment ( complete transcendence of identification using the personal ego ). One path was that taught within the sutras according to the historical teachings. One's heart of sutra practice took it's origin from morality, concentration, and wisdom ( not identifying using the personal ego ). Another path, that has become the cornerstone of Tibetan variations, was tantric. This practice blended the sutra teachings in manners adapted from Hindu systems of yoga and tantra.
Tantric systems transform the fundamental human passions of desire and aversion with regards to spiritual development. Instead of denying such primal urges, tantra purifies them into wholesome and helpful forces. It's very much like attempting to deal with an outrageous horse charging in your direction. One way is denial: set up your hands and shout out, "stop, stop!" Probably you'll be bowled over through the animal. Another, more clever, approach would be to step aside after which jump on its back because it charges past you. When this occurs, you have a opportunity to start coaxing it to maneuver in certain directions, and also over time you might be able to direct it right into a stable. Truthfully, you need some skill both in self-control and acceptance if your are to be successful with tantric work.
Tibetan Tantra ( also called the Vajrayana ) incorporates the main aspects of both Hinayana and Mahayana Buddhist teachings. It's basically an esoteric extension on these themes. Hinayana and Mahayana are two schools of Buddhist practice which have basically similar goals and methods but somewhat differing philosophies. For example, Theravadin Buddhism ( known for its Vipassana meditation ) is really a Hinayana teaching and Zen Buddhism is really a Mahayana teaching. Tantra itself has various schools which may be grouped through the relative emphasis they put on working with exoteric and esoteric practices.