The doshas are the primary forces and subtle substances behind all physiological and psychological functions, they produce the body and are the causative factors in the disease process.
Vata dosha is the biologic humor of space and air. its qualities are dry, light, cold, rough, subtle, and mobile. Vata dosha is responsible for all physiological processes, it governs the breath, sensory and nervous systems, because of vatas involvement with the nervous system vata type disorders have more severe implications than pitta or kapha as it will affect the entire body through the nervous system.
Pitta dosha is the biological humor of fire and water the fire here is a liquid fire like acid, fire by itself can't exist in the body it would destroy it, so we can say fire contained by water. Pittas qualities are hot, sharp, slightly oily, light, mobile, and liquid. pitta governs digestion, temperature, sight, hunger, and the luster of our skin.
Kapha dosha is the biological humor of water and earth kapha is the glue that holds us together it is cold, wet, sticky, heavy and dull. Kapha is the mucus lining of the stomach and lungs, the saliva in our mouths that helps to break down food and the mucus that traps invaders in our noses. Think of clay when clay has a good wet to dry ratio it is moldable and mobile, too much water and you have a gray puddle you cant do anything with, not enough water it becomes brittle and breaks easily.
All three doshas are needed in the body vata is movement and energy, Responsible for the coordination of all of the bodies functions, Pitta is our inner fire, our radiance, through which we digest impressions, thoughts, air and food, while kapha is our vigor, the internalized essence of digested air, food, mental impressions, and our mental endurance.
Keeping the doshas in balance is important and doshic balance can be maintained easily by knowing and following your dincharya (daily recommended routine) and ritucharya (seasonal routine).