These words mainly express the relationship between the viscera and organs by breathing, sound amplitude, emotional expression and mouth shape, and cooperate with the Chinese classical music syllable "Jiao Gonghui Shangyu" and the length of breathing to achieve the goal.

The initial practice can make sounds, mainly to master the length of breathing, the mouth shape of pronunciation and the direction of qi movement. No sound is allowed after proficiency.

I can't explain it clearly. Anyway, it is the wisdom and practice of our ancestors for thousands of years, so we don't need to be too serious.