This video is based on a dialogue from the Katha Upanishad between Nachiketa and Yama (the god of death). For his third boon, Nachiketa asked Yama to explain to him the mystery of what comes after death. Yama's reply explains the core of Hindu Philosophy or Advaita Vedanta i.e the doctrine of non-duality. It explains who we really are and how to realize our true self.
Story :
Vājashravasa, desiring a gift from the gods, started an offering to donate all his possessions. But Nachiketa noticed that he was donating only the cows that were old, barren, blind, or lame;[5] not such as might buy the worshiper a place in heaven. Nachiketa wanting the best for his father's rite, asked: "I too am yours, to which god will you offer me?". After being pestered thus, Vājashravasa answered in a fit of anger, "I give you to Death (Yama)".
So Nachiketa went to death's home, but the god was out, and he waited three days. When Yama returned, he was sorry to see that a Brahmin guest had been waiting so long. He told Nachiketa, "You have waited in my house for three days without hospitality, therefore ask three boons of me". Nachiketa first asked for peace for his father and himself. Yama agreed. Next, Nachiketa wished to learn the sacred fire sacrifice, which also Yama elaborated. For his third boon, Nachiketa asked to learn the mystery of what comes after death.
Yama was reluctant on this question. He said that this had been a mystery even to the gods. He asked Nachiketa to ask for some other boon, and offered many material gains.
But Nachiketa replied that material things will last only till the morrow. He who has encountered Death personally, how can he desire wealth? No other boon would do. Yama was secretly pleased with this disciple, and elaborated on the nature of the true Self, which persists beyond death. The key of the realization is that this Self (within each person) is inseparable from Brahman, the supreme spirit, the vital force in the universe. Yama's explanation is a succinct explication of Hindu metaphysics, and focuses on the following points:
The sound Om! is the syllable of the supreme Brahman
The Soul, whose symbol is Om is the same as the omnipresent Brahman. Smaller than the smallest and larger than the largest, the Soul is formless and all-pervading.
The goal of the wise is to know this Soul.
The Soul is like a rider; the horses are the senses, which he guides through the maze of desires.
After death, it is the Soul that remains; the Soul is immortal.
Mere reading of the scriptures or intellectual learning cannot realize Soul.
One must discriminate the Soul from the body, which is the seat of desire.
Inability to realize Brahman results in one being enmeshed in the cycle of rebirths. Understanding the Self leads to moksha
Thus having learned the wisdom of the Brahman from Yama, Nachiketa was freed from the cycle of births.
Source - en.wikipedia.org/wiki/Nachiketa