Agni is usually translated as fire, its attributes are transformation and creation. Its function is its ability to convert. For example, food is transformed into nutrients for better assimilation, or into waste products for elimination from the body.
In Ayurveda,Agni is the digestive capacity itself.
In our body/mind, optimal functioning of Agni can lead to balance and its incorrect functioning will create toxin (ama). Agni is a central concept for health maintenance, as it is not only responsible for absorbing nutrients, but also for destroying pathogens. Undigested food is transformed into a toxin for the body and mind and depresses the immune system. When agni works properly there is good digestion and circulation.
It is useful to personify Agni as a god to be worshiped, where the worship is the food we eat, and to ritualize the act of eating as an offering, being attentive to the needs of our digestive fire as well as to its functioning.