Padmasambhava, also known as Guru Rinpoche, is considered the founder of Tibetan Buddhism and is highly revered in the Nyingma school of Tibetan Buddhism. The relationship between Padmasambhava and the Nyingma school is deeply intertwined and has played a significant role in shaping the beliefs and practices of this school.

Padmasambhava was invited to Tibet in the 8th century by King Trisong Detsen to help establish Buddhism in the country. He is believed to have played a crucial role in the spread of Buddhism in Tibet, especially in the Nyingma school. He is also credited with the establishment of the first monastery in Tibet, Samye Monastery, which became the center of Nyingma teachings.

One of the main reasons for Padmasambhava's importance in the Nyingma school is his role as the founder of the terma tradition. Terma, meaning "hidden treasures," refers to sacred teachings and objects that were concealed by Padmasambhava and other enlightened masters for future generations. These treasures were later discovered by tertöns, or treasure revealers, who were able to access them through their spiritual practice. These teachings and objects are considered vital to the Nyingma tradition and are believed to contain the pure and uncorrupted teachings of Padmasambhava.

Padmasambhava is also considered to be an emanation of the Buddha Amitabha, the embodiment of the enlightened mind. This belief is especially prominent in the Nyingma school, where he is revered as the second Buddha, after Shakyamuni Buddha. His teachings and practices are considered essential for achieving enlightenment, and he is often depicted in Nyingma iconography alongside other important figures such as Vajrasattva and Avalokiteshvara.

Furthermore, Padmasambhava is also believed to have introduced the practice of Dzogchen, the highest form of meditation in the Nyingma school. Dzogchen, meaning "Great Perfection," is a practice that focuses on the recognition of one's true nature, the primordial state of pure awareness. This practice is considered the most direct path to enlightenment in the Nyingma tradition, and Padmasambhava is revered as the foremost teacher of Dzogchen.

In conclusion, the relationship between Padmasambhava and the Nyingma school of Tibetan Buddhism is one of deep reverence and importance. His teachings, practices, and role as the founder of the terma tradition have greatly influenced the beliefs and practices of the Nyingma school. His legacy continues to be celebrated and revered by practitioners of Tibetan Buddhism, particularly those in the Nyingma tradition.