Auras are a method of improving the benefits you gain from certain skills, like the Sharpshooter aura. Other auras are just for fun, like the Oddball aura.
All auras come with a glow effect when they are activated. Not only does this look good but it tells other players that you have an active aura.
Auras are equipped in your aura slot and can be activated by right-clicking the aura, when worn, and choosing 'Activate aura'. You can only have one aura equipped at a time.
Auras will stay active for as long as their activation time states - once activated, you cannot deactivate your aura. Auras also have a cooldown time. You will not be able to use your aura again until this time has passed.
You can see how long you have left on an aura by right-clicking the aura, when worn, and choosing 'Aura time remaining'. You can unequip your aura but this will remove any remaining time that the had left as active, and will not reset the cooldown.
You can only have one aura equipped at any one time, so choose carefully.
Other things to note about auras are that they are untradeable and some cannot be used in PvP. The PvP restrictions are mentioned in the table below.
Auras can be purchased, and replaced if they have been lost, from Xuan. You can find Xuan in Burthorpe near the Warriors' Guild.