What is "sutrayana"

Sūtrayāna, (Sanskrit) is the Indo-Tibetan three-fold classification of yanas. A yana is a Buddhist mode of practice that leads to the realization of emptiness. The three yanas of the Sutrayana are Hinayana, Mahayana, and Vajrayana. The third yana, Vajrayana, comprises Tantrayana and Dzogchen.