Vajrayana

The Vajrayana (Sanskrit: lit. The Adamantine Vehicle) school of Buddhism, practiced predominantly in Tibet, Mongolia and Bhutan, consists of a collection of techniques for the practice of Mahayana, along with the texts that expound those techniques (the Tantras). It is also known to the west as Tantric Buddhism. Being the foundation for Buddhism, it is sometimes expounded as a third and separate major school of Buddhism, alongside the Mahayana and Theravada.

There are four main schools of Tibetan Buddhism: Nyingma, Sakya, Kagyu, and Geluk. All four schools identify themselves as belonging to the Mahayana or "Great Vehicle" tradition, which dominates in China, Korea and Japan.

The techniques are characterized by:
- The use of mantras, or short verbal formulae
- Strong focus on the guru, or teacher
- A highly-developed tradition of meditation, including concentration techniques such as the visualization of bodhisattvas.

Practitioners are introduced to a collection of Vajrayana practices through a series of initiations.

These can be divided into four categories, namely,

Kriyayoga
Charyayoga
Yogatantra
Anuttarayogatantra, which is furthermore divided into "mother", "father" and "non-dual" tantras.

In the Nyingma tradition the division is sixfold:

Three Outer Tantras:
- Kriyayoga
- Charyayoga
- Yogatantra
Three Inner Tantras, which correspond to the Anuttarayogatantra:
- Mahayoga
- Anuyoga
- Atiyoga - Dzogchen

The practice of Atiyoga is divided into three classes: Mental (SemDe), Spatial (LongDe), and Esoteric Instructional (MenNgagDe).

Vajrayana, which developed in Northern India circa 7th century, has its main philosophical roots in Madhyamika of Nagarjuna, Chandrakirti and Vijnanavada (aka Yogachara), Chittamatra) of Asanga, and Vasubhandu. The most famous teacher of Vajrayana is Guru Padmasambhava.