Water is a common example of an amphiprotic substance. It can donate a hydrogen ion to become OH- or accept one to become H3O+.
Zwitterion: This is a molecule that contains both positive and negative charges, but is overall neutral. Like our versatile soccer player, it has the ability to react in different ways under different conditions.
A solution that resists changes in pH when small amounts of an acid or base are added. These often contain amphiprotic substances which help maintain this balance.