The difference between sentient beings and Buddhas is that the first has obscurations while the other does not. We are sentient beings because we have temporary “defilements” or obscurations to our wisdom mind. All sentient beings are inherently Buddhas, temporarily defiled by gross emotional obscurations and by the subtle obscuration of habit. When these are removed, the Buddha within naturally manifests. According to the Vajrayana path, only two methods exist for removing these two obscurations: first, accumulation of merit and wisdom, and second, the direct transmission from the guru’s mind to the student’s mind. Ngondro uses both methods and includes the essential practices of the Three Yanas (vehicles) Hinayana, Mahayana, and Vajrayana. The essence of Hinayana practice is refuge. The generation of Bodichitta (enlightened attitude) is the essence of Mahayana practice. Accumulation, purification and the mind transmission of Guru Yoga are the essences of Vajrayana practice. Ngondro is a preliminary practice containing all paths, including the creation and perfection stages of the Vajrayana practice.
Since it contains all paths to the realization of enlightenment, then, every effort should be made to complete Ngondro in order to fully cultivate and realize its profound benefits.“A commentary on the Dudjom Tersar Ngondro
The Preliminary Practice of the New Treasures of Dudjom
by Lama Tarchin Rinpoche