From Regamening Wiki

Light is the element of life and restoration. Not necessarily a "good" element, but it is in opposition to dark. If Dark represents the end, then it is Light that represents the start. Light is used to heal and revive, and not so much do damage. It is incapable of inflicting negative ailments on an enemy.

Light is the element of Magic Defense, and is weak to, and also effective against Dark. Light's weakest stat is Luck.