Tibetan Buddhism is deep and vast. For instance, Tibetan Buddhism preserves the 1,189 Sutras and 3,378 Shastras.
Another way of seeing Tibetan Buddhism, is that it preserves the Hinayana, Mahayana and Vajrayana teachings of Buddha Shakyamuni.
Tibetan Buddhism holds a great and long tradition of Buddhism. This quality is lineage. Lineage means that the teachings of Buddha Shakyamuni are preserved for their original purpose.
All happiness and suffering that we experience are due to our self-centeredness. We learn and practice Tibetan Buddhism because the Buddha’s teachings can subdue our self-centeredness permanently.
Lineage ensures that the vast teachings of Buddha Shakyamuni remain alive and practiced in this way.