Auras

All living things eliminate a unique invisible energy, life force, or aura. It closely surrounds the being, and traces can linger after the being is gone. The aura may linger for a period of time around a dead body.

Everyone and everything has a distinct aura, and an individual's aura can change over time. It takes an experienced caster to be able to identify different subjects in this manner, but it's possible with practice. Auras can be experienced in many ways when they are revealed - color, texture, motion, warmth, rigidity, size, etc. There's not a clear correlation between the quality or strength of an aura and magical potential.

Some wix can sense auras naturally to some extent, but most require the use of a spell such as Homenum Revelio or Aura Perciperium. Auras are used in Divination.

Non-living things do not have auras. Enchanted objects can have a magical energy surrounding them, but it is not the same as an aura.

At Absit Omen

"Auras," Athena supplied. Cepheus looked closer to fainting than he had earlier. "Fades quickly after check-out, according to what I've read. And I'm not sure it's unique to our folk." [1]