Deity yoga in the context of "Mirage"

Vajrayāna (Sanskrit: वज्रयान, lit. 'Diamond Vehicle or Thunderbolt Vehicle'), otherwise known as Mantrayāna ("Mantra Vehicle"), Guhyamantrayāna ("Secret Mantra Vehicle"), Tantrayāna ("Tantra Vehicle"), Indo-Tibetan Buddhism, Tantric Buddhism, and Esoteric Buddhism, is a Mahāyāna Buddhist tradition that emphasizes esoteric practices and rituals aimed at rapid spiritual awakening. Emerging between the 5th and 7th centuries CE in medieval India, Vajrayāna Buddhism incorporates a range of techniques, including the use of mantras (sacred sounds), dhāraṇīs (mnemonic codes), mudrās (symbolic hand gestures), mandalās (spiritual diagrams), and the visualization of deities and Buddhas. These practices are designed to transform ordinary experiences into spiritual paths toward enlightenment and liberation, often by engaging with aspects of desire and aversion in a ritualized context.

A distinctive feature of Vajrayāna Buddhism is its emphasis on esoteric transmission, where teachings are passed directly from teacher (guru or vajrācārya) to student through initiation ceremonies. Tradition asserts that these teachings have been passed down through an unbroken lineage going back to the historical Buddha (c. the 5th century BCE), sometimes via other Buddhas or bodhisattvas (e.g., Vajrapani). This lineage-based transmission ensures the preservation of the purity and effectiveness of the teachings. Practitioners often engage in deity yoga, a meditative practice where one visualizes oneself as a deity embodying enlightened qualities to transform one's perception of reality. The tradition also acknowledges the role of feminine energy, venerating female Buddhas and ḍākiṇīs (spiritual beings), and sometimes incorporates practices that challenge conventional norms to transcend dualistic thinking.

Chinese Esoteric Buddhism refers to traditions of Tantra and Esoteric Buddhism that have flourished among the Chinese people. The Tantric masters Śubhakarasiṃha, Vajrabodhi and Amoghavajra, established the Esoteric Buddhist Zhenyan (Chinese: 真言, "true word", "mantra") tradition from 716 to 720 during the reign of Emperor Xuanzong of Tang. It employed mandalas, mantras, mudras, abhiṣekas, and deity yoga. The Zhenyan tradition was transported to Japan as Tendai and Shingon Buddhism by Saichō and Kūkai, as well as influencing Korean Buddhism and Vietnamese Buddhism. The Song dynasty (960–1279) saw a second diffusion of Esoteric texts. Esoteric Buddhist practices continued to have an influence into the late imperial period and Tibetan Buddhism was also influential during the Yuan dynasty period and beyond. In the Ming dynasty (1368–1644) through to the modern period, esoteric practices and teachings became absorbed and merged with the other Chinese Buddhist traditions to a large extent.

In Chinese these traditions are also termed Mìjiào (Chinese: 密教; Esoteric Teaching), Mìzōng (密宗; "Esoteric Tradition") or Tángmì (唐密; "Tang (Dynasty) Esoterica").

In Tibetan Buddhism, Ngöndro (Tibetan: སྔོན་འགྲོ།, Wylie: sngon 'gro, Sanskrit: pūrvaka) refers to the preliminary, preparatory or foundational practices or disciplines (Sanskrit: sādhanā) common to all four schools of Tibetan Buddhism and also to Bon. They precede deity yoga.

The preliminary practices establish the foundation for the more advanced and esoteric Vajrayana sādhanā which are held to engender realization and the embodiment of Dzogchen, Heruka and Mahamudra.

A yidam or iṣṭadevatā is a meditational deity that serves as a focus for meditation and spiritual practice, said to be manifestations of Buddhahood or enlightened mind. Yidams are an integral part of Vajrayana, including Tibetan Buddhism, Chinese Esoteric Buddhism and Shingon, which emphasize the use of esoteric practices and rituals to attain enlightenment more swiftly. The yidam is one of the three roots of the inner refuge formula and is also the key element of deity yoga. Yidam is sometimes translated by the term "tutelary deity".

A yidam is considered to be a manifestation of enlightened qualities and a means to connect with specific aspects of the enlightened mind. The yidam is visualized during meditation in intricate detail, with the aim of internalizing its qualities and attributes. This practice is intended to facilitate the practitioner's transformation and realization of their own innate enlightened nature. It is believed to help purify the mind, accumulate positive karma, and ultimately lead to the realization of emptiness and the nature of reality.