Tridoshas are Vatta, Pitta, Kapha.
Panch Mahabhutas form chemistry of man as well as universe. Vayu and Akash combine to form Vata dosha. Tej and Aap combine to form Pitta dosha. Prithvi and Aap combine to form Kapha dosha.
Doshas are three pillars on which whole body relies.
They form basic bio-chemistry of our lives. Kapha represents the structural mechanisms and Pitta represents the functional and bio-conversional mechanisms. Vata represents the regulatory mechanisms that makes both Pitta and kapha work.
Normality of doshas balances physiology of body.
Doshas are affected by environment, work, stress, thoughts, age, lifestyle, food, etc. Once this doshas are vitiated they in turn vitiate dhatus and malas resulting in diseases. Every individual is born with particular type of dosha predominance which remains throughout his life. It forms his Prakriti. Prakriti is individuals natural constitution. i.e., genetic constitution.