Ayurveda says there are two levels within us that must be coordinated and balanced in order for us to be healthy. The first level we are all familiar with. It is the material level of cells, tissues and organs. But Ayurveda describes how the material level is actually just an expression of biological intelligence and that biological intelligence is a subset of the intelligence at the basis of all natural phenomenon. According to Ayurveda the intelligence level creates and controls the material level. Modern medicine diagnoses and treats the material level of cells, tissues and organs. Ayurveda diagnoses and treats the intelligence level. This is the difference between the two systems. 

The Divisions of Biological Intelligence: Vata, Pitta and Kapha: Biological intelligence in the human being has three subdivisions which control the various activities of the physiology. These three divisions are Vata, Pitta and Kapha - the three doshas.

Constitution (Prakriti) of a person emerges due to these three dosas (Dosas are the material substances that present within our body in a definite proportion) - vata, pitta, & kapha present in sperm & ovum at the time of fertilization. When these three vata, pitta & kapha live in equal state than constitution too remains in equilibrium and this type of constitution is best. Constitution produced from two dosa like vata-pitta, vata-kapha, kapha-pitta are not so good. Dosas plays a lead role in the formation of constitution of a person, because of these dosas whole life constitution of person remains alike and these constitutions never cause harm to that person. All these three dosas nourishes body doing their normal functions in their normal state and in their abnormal state they produce several disorders in body.  In case of favourable environment of food and activities dosa also Increases and in such situation they causes disorders.