Yin and yang represent all the opposite principles one finds in the universe. Under yang are the principles of maleness, the sun, creation, heat, light, Heaven, dominance, etc. Under yin are the principles of femaleness, the moon, completion, cold, darkness, material forms, submission, etc. Each of these opposites produces the other. Heaven creates the ideas of things under yang, the earth produces their material forms under yin, and vice versa. Creation occurs under the principle of yang. The completion of the created thing occurs under yin, and vice versa. And so on, and so on.
This production of yin from yang and yang from yin occurs cyclically and constantly, so that no one principle continually dominates the other or determines the other. All opposites that one experiences—health and sickness, wealth and poverty, power and submission—may be explained in reference to the temporary dominance of one principle over the other. Since no one principle dominates eternally, that means that all conditions are subject to change into their opposites.
Two important features of the relationships between opposites:
The cyclical nature of yin and yang, the opposing forces of change in the universe, means several things. First, all phenomena change into their opposites in an eternal cycle of reversal. Second, since the one principle produces the other, all phenomena have within them the seeds of their opposite state, for example, sickness has the seeds of health, health contains the seeds of sickness, wealth contains the seeds of poverty, etc. Third, even though an opposite may not be seen to be present, since one principle produces the other, no phenomenon is completely devoid of its opposite state. One is never really healthy since health contains the principle of its opposite, sickness. This is called "presence in absence." Once you have this principle down, the particular Chinese view as expressed in literature becomes clearer.