Vajrayana Buddhism or Tibetan Buddhism is the form of Buddhism practiced in Tibet and has The Dalai Lama as its head.
Vajrayana Buddhism is also known as Tantric Buddhism, Mantrayana and Esoteric Buddhism. Many view this as the third major school in Buddhism, after the Theravada and Mahayana schools, although it really is just a subset of the Mahayana school. The Buddhists that follow this path usually consider it to be the final stage in the evolution of Buddhist theory. There are two major subsets of this school of thought: Tibetan Buddhism and Shingon Buddhism. The main difference with this school of thought versus the others is that it is considered to be an accelerated path to the obtainment of enlightenment.
It is a blending of Mahayana Buddhism and the native shamanism of Tibet. Vajrayana Buddhism has become more popular in the West as a result of missionary activities of Tibetan monks wishing to save their culture from the depredations of Chinese Communists. It shares all of the Bodhisattva ideals and desire for compassion with the Mahayana school and adds many sophisticated psychological techniques and meditations / visualizations.