This essentially is the power system of the world that measures someone's strength in certain aspects. The demon race is the only one who has a sixth sense for this naturally, the royals being more sensitive to it, but others must have some sort of modification (spells, potions, etc) to be able to get this information.

For alterations, there are aura maskers and benders. Maskers cover up the aura entirely, which was used commonly against the demon race, and benders made the individual's aura either seem strengthened or weakened for a false front. These things were typically imbued into wearable objects like pins, jewelry, belts, etc.

This term WAS mainly used to refer to the demon and divine races, as these two were the ones who had a stronger average auras in all categories before the end of the Blood War. Although- there were groups in each race that were particularly gifted in one or more areas.

Currently, the fairies and elves are referred to by this term as their mental and magical strengths are much higher than the average human's.