In some schools this is a certificate and a formal ceremony stating that you’re now the Dharma heir of so-and-so. It’s described as a mind-to-mind transmission that has continued uninterrupted from Sakyamuni Buddha himself, and only someone who has received this is an authentic inheritor of the Dharma.
However, Korean Buddhism has a rather different perspective on this.
In traditional Korean Buddhism, there are no certificates of transmission. After ten or twenty years, a general consensus would arise that someone was the Dharma successor of their teacher. Their authority was derived from their ability, not a piece of paper.
Likewise, people didn’t really buy into the idea of an unbroken lineage. There could be periods where there were a number of great teachers, where there was only one, and even generations where there was no particularly outstanding teachers. The Supreme Patriarch of Korean Buddhism, Hanam Sunim (1876-1951), explained why this wasn’t a problem:
It doesn’t matter whether or not you knew the previous king. If you sit on the throne, you’re now king.
That is, if you awaken to the inherent Buddha-essence within you, you are the successor of Sakyamuni.
We each this very same mind as Sakyamuni, inherent within us at every moment and every place. Our job then, is to learn to rely on this, even though it’s indistinct at first. If we can diligently do this, we will have the kinds of experiences that will confirm we are going in the right direction, and which will reveal our direction.
Continuously letting go and entrusting everything to this Buddha-mind is the path forward as well as a great Dharma protecting warrior, because in returning everything we experience, including what we know and what we don’t know, we keep letting go of “I” and “me”, and are not caught by the experiences that could serve as toeholds for pride, greed, and fear.