If you walk down the drink aisle in the supermarket, you'll find tonic water, seltzer, soda water and sparkling water. Although soda water and sparkling water look, taste and smell the same, there are a couple of substantial differences.
Soda water and sparkling water contain the same ingredients - water mixed with sodium bicarbonate. The difference between them isn't what, it's how - soda water's sodium bicarbonate is added, whereas sparkling water naturally contains sodium bicarbonate.
Natural sparkling water usually contains a wide array of minerals compared to artificial soda waters and seltzers, which only contain sodium bicarbonate (otherwise known as carbon dioxide).
Soda water is marketed as a cocktail mixer, while sparkling water is promoted as a more upscale version to be drunk on its own. For that reason, it is generally more costly than soda water.