Until Mao, if he wishes to, shows up to gives us more details about Jindan here is a nice article: Jindan (Golden Elixir) - From The Encyclopedia of Taoism
Authors of alchemical texts often call their tradition the Way of the Golden Elixir (jindan zhi dao ).
Gold (jin ) represents the state of constancy and immutability beyond the change and transiency that characterize the manifested world.
As for dan , or “elixir,” lexical analysis shows that the semantic field of this term — which commonly denotes a variety of red — evolves from a root-meaning of “essence,” and that its connotations include the reality, principle, or true nature of an entity, or its most basic and significant element, quality, or property.
Chen Zhixu and other authors emphasize that the inner elixir is possessed by every human being, and is a representation of one’s own innate realized state. Liu Yiming (1734-1821) expresses this notion as follows:
Human beings receive this Golden Elixir from Heaven. . . .
Golden Elixir is another name for one’s fundamental nature, formed out of primeval inchoateness (huncheng, a term derived from the Daode jing). There is no other Golden Elixir outside one’s fundamental nature. Every human being has this Golden Elixir complete in himself: it is entirely realized in everybody. It is neither more in a sage, nor less in an ordinary person. It is the seed of Immortals and Buddhas, and the root of worthies and sages. (Wuzhen zhizhi, chapter 1)