Soda water has the longest historical roots, according to Slate. When artificially carbonated water first hit the market in the late 18th century, it was called “soda water.” The site writes that you could call soda water “seltzer.” Both are, simply, water with carbon dioxide. As Eater points out, the absolute plainness of seltzer is what makes it such a perfect canvas for so many brands to add flavors and/or alcohol.
The important distinction between “seltzer” and “sparkling water” is where the bubbles come from. Artificially carbonated water is “seltzer,” explains My Recipes. Meanwhile, brands like La Croix are “sparkling water,” says People. Sparkling water’s carbonation is natural. The FDA regulates seltzer as a “soft drink” and sparkling water as “bottled water.” One more wrinkle is that “mineral water” can be either flat or sparkling, as long as it comes from a mineral spring. Perrier and San Pellegrino, writes People, “are sparkling mineral waters.”
“Club soda” has extra ingredients. It’s artificially carbonated water with added sodium and/or potassium salts, meant to neutralize acidity and actually taste more natural. Finally, “tonic water” isn’t even water! It’s a sweetened soft drink with carbonated water. So, soda water is basically seltzer and falls under the carbonated/bubbly water umbrella; but minor tweaks make it different enough from sparkling water, club soda, and tonic water that it pays to know the distinctions when you’re shopping or ordering.