The Tao is the way: the source from which things arise, the pattern by which they change, and the course a thing follows when nothing obstructs it. The Tao Te Ching opens by warning that the Tao that can be spoken is not the constant Tao, and the tradition takes that seriously. Its central term is approached mostly by indirection, through images of water, the uncarved block, the valley, the infant.
Wu wei is the corresponding practice. It is usually rendered as non-action, which misleads; it means acting without forcing, in accordance with the grain of a situation rather than against it. The political application in the Tao Te Ching is a ruler who governs by not interfering, and much of the text is addressed to rulers. The personal application is a way of moving through the world that expends nothing on struggle.
Ziran, self-so or spontaneity, names what is left when the forcing stops. De, often translated as virtue or power, is the Tao as it is present and effective in a particular thing.
The Zhuangzi works quite differently from the Tao Te Ching. It argues by story, joke and paradox, questions whether any perspective is privileged, treats death as a transformation rather than a loss, and is sceptical about the usefulness of the distinctions people insist on. Where the Tao Te Ching is aphoristic and often political, the Zhuangzi is discursive and much harder to reduce to doctrine.
The complementary polarity of yin and yang, and the correlative cosmology of the five phases built around it, are not exclusive to Taoism; they belong to a shared Chinese framework used by Confucian and medical writers as well. Taoist thought and practice, however, make particularly heavy use of them.