But the core practice of Vajrayana, in whatever form, is “deity yoga,” in which one performs meditation and ritual actions and visualizations in order to enter into union with a particular Vajrayana deity.
In this way, one’s own body is transformed into the body of a Buddha, although one ideally chooses to be only a bodhisattva until all other beings have been helped to enlightenment.
In Tantric guru yoga, one does the same thing, but concentrates on becoming the same as the teacher—adopting the ritual practices and wisdom of that teacher.