One emulates, or seeks a close spiritual relationship with, the Buddhist deity or magical guru in these rituals. In Tibetan tradition, Buddhist spiritual leaders and teachers are called “lamas.”
The goal of the Vajrayana practitioner, as in Mahayana, is to become a bodhisattva.
That means that one seeks enlightenment, but postpones final nirvana so as to stay in the world of samsara and help others reach nirvana first.
This is of course different from Theravada, where one aspires to be an arhat (one who attains enlightenment and then never comes back to samsara).