Dharma can be divided into three: the outer nature, the inner nature, and the secret nature of phenomena

We can divide it into three things to understand the nature of phenomena: the outer nature, the inner nature, and the secret nature of phenomena. And the outer nature of, for example, Samsara is suffering, and the renunciation taught in the Hinayana and Mahayana teachings.
And then Mahayana teachings, like the Second Turning of Dharma Wheel, the Great Mother Wisdom, Paramita teach us how to recognize the inner nature of phenomena, which is emptiness; and then Tantrayana teaches the realization of the secret, the great secret nature of phenomena, which is more like awareness, a unity of awareness and emptiness.

Cited “Today Dzogchen is Practiced by More and More Lay People”, Hungkar Dorje Rinpoche

Dieu Am cites.