The main difference between club soda and seltzer is that seltzer lacks some of the ingredients that club soda contains. Club soda also has a much more acidic pH level than seltzer and may contain baking soda.
One of the differences consumers may be able to taste is the sodium content in club soda versus seltzer. Seltzer may sometimes taste very dull and flat, given that it is made up of just two ingredients: water and carbon dioxide. Carbon dioxide is what provides the "fizz" or carbonation in both seltzer water and club soda. Seltzer may be healthier to consume, while club soda offers a heartier flavor.