Seltzer is known to be carbonated water. This means that it is water that has been mixed with carbon dioxide in order to create the type of fizz that you may want. This does not contain any added minerals anymore. Sparkling water is known to be naturally carbonated and this usually comes from spring or well.
Some people also confuse these two with club soda because this also has fizz. Club soda gets its fizz sodium salts. Some club sodas also have potassium salts. Usually, these ingredients need to be added in order to provide the needed fizz of these drinks. Which among the choices do you normally like the most?