An aura is a rune that gives a stat bonus to all nearby party members while active. An active aura reserves a percentage of the caster's max mana, and can be toggled when the cooldown is ready.
Auras are disabled when dying, rezoning, switching characters, or logging in/out. Teleporters within the same zone usually don't remove auras.
Characters can have multiple auras of any or the same type equipped and active. Copies of auras in parties stack additively an unlimited number of times.