Al2O3 is an example of a neutral oxide.
Al2O3, aluminium oxide is amphoteric. When it is added to the base, it acts as an acid and when it is added to the acid, it acts as a base.
An amphoteric oxide is an oxide that can act either as an acid or as a base to create salt and water in a reaction.
The oxidation states open to a chemical species are based on amphoterism. Amphoteric oxides and hydroxides are formed when metals have several oxidation states.