The difference in tea quality and character is primarily because of the process. This difference also reflects on the chemical changes in tea leaves, especially the change of flavonoids.
This blog post is the synopsis and reading notes of the article Tea Classification in Theory and Practice by Professor Chen Chuan, translated by Michael Salt, librarian, East Asian History of Science Library, Cambridge (Journal d’agriculture traditionnelle et de botanique appliquée Année 1981 28-3-4 pp. 329-344).
Watch the Youtube video for the full walkthrough.
The link to the translated article is in the description box on Youtube.
P.337, para.2. “yellow alkane alcohols” in this article refer to flavonoids.
P.337, para.3. “dry vet”, “wet vet” are vague translations and descriptions of the tea process. Be aware, and not take these words too lierally.
P.337, para.4. “on customary application” points out the classification respects the existing naming that has arisen from the tea farmers and producers.