Yoga is not just the physical exercise. To use yoga in therapeutic way one must know that how disease occurs in the body. And to know how disease occurs there is Panchakosha (5-layer) concept. Here I shall start with the concept of Panchakosha.
Panchakosa (Sanskrit: पञ्च कोश; “five sheaths”) from root pancha, “five” + kosha, “body” — is the “five bodies,” or discernible “aspects” of man, arranged successively from the grosser to the increasingly more subtle.