What do you mean by eight-character hiding?

Tibetan stalk is a eight-character term, which refers to the expression of some kind of heavenly stems hidden in the ground branches.

That is, a group of heavenly stems and earthly branches can be divided into three parts: heaven, earth and man. The sky is sunny, the earth is cloudy, and people are between heaven and earth. So the heavenly stems are Tianyuan, the earthly branches are earthy branches, and the earthy branches are earthy branches.