An Aura is an AoE skill that can provide a constant buff to your party members or debuff to your enemies.
Auras will be usable by the Monk class in Diablo III. However, unlike the Paladin's auras in Diablo II, they will have a short duration and must be reactivated to provide their benefits. In some cases they may also have instant effects.
Auras in Diablo II are primarily used by the Paladin class, but can also be granted by special equipment and hirelings. If the aura is granted from a skill, the Paladin can only have one such aura active at a time. Multiple auras are stackable if they originate from different sources such as other members in the party, their mercenaries, or their equipment.