What are the main differences between yin and evil, evil yin and true yin?

True yin, the most fundamental vaginal fluid in the human body, belongs to something that maintains the human mechanism. The human body pays attention to the balance of yin and yang. Where there is yang, there is yin and evil yin. Pathogens are exogenous six pathogens, and wind, cold and summer are damp and hot, which will make people sick. Yin and Yang are opposite, fire is Yang, and cold is Yin. Simply put, evil yin can make people sick, and true yin is one of the fundamental needs of the human body.