Within the body, every phenomenon is a product of the interaction of Blood, Moisture and Qi. Moisture is an amorphous substance as well as the process of generating, distributing and storing fluid. Without proper Moisture, the Qi becomes hot and agitated and the Blood dries up and congeals.
Just as the Earth is comprised of land, ocean and atmosphere, so the body is organized as Blood, Moisture and Qi. Qi governs the shape and activity of the body and its process of forming and organizing itself. Blood governs tissue, the material form of the body. Moisture governs the internal environment, the body's inner ocean. Moisture and Blood are both Yin in quality and sometimes talked about together, under the name Blood. Moisture is the intermediate state of Blood generating to Qi and Qi transforming Blood.
Lack of Moisture manifesting as cracked skin or scanty urine is a symptom of Dryness. This may be caused by a dry climate (an external pernicious influence) or may simply mean that the body is unable to properly distribute its own Fluids. A person with diabetes, for instance, can drink a great deal of water and still remain very thirsty because the body is unable to retain the fluid.