Kriya and Carya Tantra
In the 13th century, Tibetans developed a four-fold classification system for Tantric texts based on the type of practices each contained.
Briefly, these are sub-divided into the lower tantras of Kriya (action) and Carya (performance) and higher tantras of Yoga and Anuttara Yoga.
Practitioners of Kriya Tantra regard themselves and the deities as separate entities, where they are the “servants” of the deities and offer acts of devotion involving the body speech and mind.
In Carya Tantra, a practitioner holds the similar view of self and deity as separate entities, but utilises both external and internal activities (hence known as performance).
The higher tantras identify practitioners dynamically as the deity, whereby in Yoga tantra, a practitioner generates a vivid appearance of the deity and then absorb the deity into himself.
In Anuttara Yoga, the practitioner transforms himself into the deity.