Prana is a Sanskrit word denoting the energy that surrounds us, surrounds the earth, surrounds the solar system and present everywhere in the entire universe. It is known as Chi by the Chinese, Ki by the Japanese, Manna by the Polynesians and was introduced to the Western world as Life Force Energy.
Prana can be called a sum total of all the Energies which is keeping all components of this universe in continuous vibration and giving life to all beings.
We are body, mind and soul. The physical body comprising of visible parts, internal organs, fluids and all systems inside are the Gross Component of our body. For the Gross Body to sustain, to exist and to be healthy, it requires prana which would be sum total of the soul, the mind, the chakras, the nadis and the subtle body or aura around the physical body . As long as we have abundance of prana the body will be healthy and when prana becomes depleted and negative energies take charge of the body, it will become weak and sick.