Some people think Vajrayana Buddhism is very mysterious. This is because they lack an understanding of the Vajrayana system of thought and practice. In fact, it is not at all mysterious; it is just that the methods are very special, very fast, and relatively easy to practice. To comply with the teachings, a Vajrayana practitioner should progress along the path from aspiration to attainment of buddhahood in stages. 

Depicted from GATEWAY TO VAJRAYANA PATH - Entering the Vajrayana Path