Yin originally meant "shady, secret, dark, mysterious, cold." It thus could mean the shaded, north side of a mountain or the shaded, south bank of a river. Yang in turn meant "clear, bright, the sun, heat," the opposite of yin and so the lit, south side of a mountain or the lit, north bank of a river. From these basic opposites, a complete system of opposites was elaborated. Yin represents everything about the world that is dark, hidden, passive, receptive, yielding, cool, soft, and feminine. Yang represents everything about the world that is illuminated, evident, active, aggressive, controlling, hot, hard, and masculine. Everything in the world can be identified with either yin or yang. Earth is the ultimate yin object. Heaven is the ultimate yang object. Of the two basic Chinese "Ways," Confucianism is identified with the yang aspect, Taoism with the yin aspect.

Although it is correct to see yin as feminine and yang as masculine, everything in the world is really a mixture of the two, which means that female beings may actually be mostly yang and male beings may actually be mostly yin. Because of that, things that we might expect to be female or male because they clearly represent yin or yang, may turn out to be the opposite instead.

Taoism takes the doctrine of yin and yang sees all change as one opposite replacing the other. The familiar diagram of Yin and Yang, the , the "Great Ultimate" [Wade-Giles T'ai-chi] diagram, shows the opposites flowing into each other. The diagram also illustrates, with interior dots, the idea that each force contains the seed of the other, so that they do not merely replace each other but actually become each other. (The earliest attested example of the diagram, strangely enough, occurs on a Roman shield illustrated in the fifth century Notitia Dignitatum.)

Yin and yang are descriptions of complementary opposites rather than absolutes. Any yin/yang dichotomy can be seen as its opposite when viewed from another perspective. The categorisation is seen as one of convenience. Most forces in nature can be broken down into their respective yin and yang states, and the two are usually in movement rather than held in absolute stasis.

Shiva Shakti, the Sacred Marriage of Parvati and Lord Shiva, depicts a condition of enlightenment where male and female human principles, anima and animus, yin and yang, are perfectly combined in a balanced way. In this image, the union of Shiva and Shakti expresses the sacredness as a path to spiritual union. Tantric Yoga is also based on the belief that the Universe is made up of Yin-Yang (Female-Male) principles, and that these Yin-Yang energies are also contained within the human body. Unification and harmonization of the Yin and Yang energy forces brings the experience of joyous transcendence and mystical ecstacy.

The two great principles Yin and Yang which are respectively male and female, run through the whole universe and everything which exists was believed to depend on their interplay and combinations with each other. Resemblance can be found in Hinduism were the universe is believed to be consisting of the interaction of two great forces personified as male and female deities; Shiva and Sakti. In the universe, they are generally regarded as parts of something greater, of a sublime and mysterious one, which unites and transcends them. Striking examples of the union of male and female energy are represented in tantric Buddhist art, where the physiological act of sex greatly increases suggestibility. The images of Bodhisattvas, protectors and other gods depicted in sexual embrace (yab-yum) with their saktis, are creations of a greater being, a union more powerful in order to accomplish its task. These wonderful works in Asian art reveal a spiritual artistic level and represent a deeper meaning than just decorative value or pleasing aesthetic quality. They create a sense of organic rhythm and dynamic force and exhibit the emotional inseparability between female and male, reaching a level were art is suggestive of an existing unlimited universe.