Yidam in the context of "Three Roots"

The fundamental practice of Vajrayana and Tibetan tantra is deity yoga (devatayoga), a form of Buddhist meditation centered on a chosen deity or "cherished divinity" (Skt. Iṣṭa-devatā, Tib. yidam). This involves the recitation of mantras and prayers alongside the detailed visualization of the deity and their mandala—a sacred configuration that includes their Buddha field, consorts, and attendant figures. The 14th-century scholar Tsongkhapa stated that deity yoga is the distinctive feature that sets Tantra apart from the Sutra-based path.

In the highest class of Tantras, the Unsurpassed Yoga Tantras, deity yoga is typically practiced in two stages: the generation stage (utpatti-krama) and the completion stage (nispanna-krama). In the generation stage, practitioners dissolve ordinary perception into emptiness and then re-imagine reality through the form of a fully enlightened deity, understood as an expression of ultimate truth. The deity is visualized as “empty yet apparent,” like a mirage or rainbow, never solid or objectively real.

Kālacakra (Tibetan: དུས་ཀྱི་འཁོར་ལོ།, Wylie: dus kyi 'khor lo) is a polysemic term in Vajrayana Buddhism and Hinduism that means "wheel of time" or "time cycles". "Kālacakra" is also the name of a series of Buddhist texts and a major practice lineage in Indian Buddhism and Tibetan Buddhism. The tantra is considered to belong to the unexcelled yoga (anuttara-yoga) class.

Kālacakra also refers both to a patron tantric deity or yidam in Vajrayana and to the philosophies and yogas of the Kālacakra tradition. The tradition's origins are in India and its most active later history and presence has been in Tibet. The tradition contains teachings on cosmology, theology, philosophy, sociology, soteriology, myth, prophecy, medicine, and yoga. It depicts a mythic reality whereby cosmic and socio-historical events correspond to processes in the bodies of individuals. These teachings are meant to lead to a transformation of one's body and mind into perfect Buddhahood through various yogic methods.