Original: Carbonated water, also known as sparkling water, fizzy water, seltzer, and water with gas, (collectively as an aerated beverage), is plain water into which carbon dioxide gas has been dissolved, and is the major and defining component of most soft drinks.
Simplified: Carbonated water, also known as sparkling water, fizzy water, seltzer, and water with gas, is plain water into which carbon dioxide gas has been dissolved.