AdBlue is the trademarked name for a 32.5% solution of urea (CH4N20) in demineralised water, as defined by the international standard IS022241 for AUS (Aqueous Urea Solution) 32.
The trademark belongs to the German automobile industry association (VDA), and any company calling its product AdBlue has to meet strict quality standards.
AdBlue® is non-toxic and safe to handle. It is not a fuel or a fuel additive and should only be used in the dedicated tank in your vehicle. It is refilled in a similar way to refuelling diesel.