You can sense the presence of evil. The amount of information revealed depends on how long you study a particular area or subject.
1st Round: Presence or absence of evil.
2nd Round: Number of evil auras (creatures, objects, or spells) in the area and the power of the most potent evil aura present.
If you are of good alignment, and the strongest evil aura’s power is overwhelming (see below), and the HD or level of the aura’s source is at least twice your character level, you are stunned for 1 round and the spell ends.
3rd Round: The power and location of each aura. If an aura is outside your line of sight, then you discern its direction but not its exact location.
Aura Power: An evil aura’s power depends on the type of evil creature or object that you’re detecting and its HD, caster level, or (in the case of a cleric) class level; see the accompanying table. If an aura falls into more than one strength category, the spell indicates the stronger of the two.