Ayurveda is the traditional healing system of India. As a totality, with all of its nuances, it is complex. However, at its most basic, it revolves around balance.
It recognizes five elements (earth, water, air, fire, and ether), twenty qualities (things like hot/cold, oily/dry, smooth/rough), and three “doshas.” These three doshas are probably the most familiar part of Ayurvedic thought in the West.
The doshas are vata (considered air + ether), pitta (fire + water), and kapha (water + earth). Each is characterized by a particular subset of the qualities. For instance, vata is light, dry, cold, etc. Although each person is believed to have an innate constitution characterized by the dominance of a particular dosha or pair of doshas, the goal is to seek balance, and imbalance is viewed as the cause of disease.
Because Ayurveda arose in ancient India, and it is a holistic system, Ayurveda and Hinduism have largely been intertwined. This may make some Christians uncomfortable. The basic principles of balance, however, appear to be a common thread among all traditional healing systems and can be potentially considered independently of Hindu religious thought.
Some of the principles, although typically applied in a fairly complex manner, seem like common sense when we really stop to think about it. If one is out of balance in the direction of being too cold, the solution would be to add heat (through food or other controllable factors). If too dry, add moisture. And so on. These principles may be employed by anyone, but if you are interested in more complex Ayurvedic balancing, you probably want a trained practitioner.
Dr. Douillard is a very common-sense, well-balanced (ha!) source of information from a Western Ayurvedic perspective.