Wikipedia
Mahayoga
Mahāyoga (Skt. "great yoga") is the designation of the first of the three Inner Tantras according to the ninefold division of practice used by the Nyingma school of Tibetan Buddhism.
Mahāyoga is held to emphasize the generation stage (or "development stage") of Tantra, where the succeeding two yana, anuyoga and atiyoga, emphasise the completion stage and the synthesis or transcendence of the two, respectively.