Human body has five sheaths or layers.
Annamaya Kosa, Of Food,
Pranamaya Kosa,of Vital Breath,
Vijnanamaya Kosa, of Knowledge,
Manomaya Kosa , of Mind and
These five layers surround the Atman,the individual self.
Annamaya Kosa is made up of the essence of Food, not food itself.
The food we eat gets digested and its essence. called the Rasa and it sustains the body.
Food determines our thoughts and dispositions-read my post on this under Hinduism.
We become what we eat for we think because of what we eat and we become what we think.( Bhagavad Gita)
Prana is the subtle breath, not actual air.
It is the subtle quality of air.
Breath regulation is taught is Yoga;people mistake control of air.
Breath has three aspects,
It is puraka when inhaled(through the left nostril)
It is also called the Ida Nadi.
Rechaka is drawn through the right nostril, Pingala Nadi.
When retained in the lungs it is Kumbhaka.
The ratio of Pranayama, of breath control is 1:4:3-Puraka:Kumbhaka:Rechakam.
Mind is the other layer.
Thought ways determine what we think and what we think decide what we are and what we become.
Through right food and right breath control, right mental disposition can be attained.
Vijnana or Knowledge is another layer, made of two types of knowledge.
Para Vidya, Knowledge of the Reality, which is eternal, correct .