Carbonated waters?

After failing to find sugar-free peppermint torani syrup at Cost Plus yesterday, it occurred to me that I could make italian sodas (one of my favorite treats) and italian cream sodas (a favorite of Scott’s) at home pretty easily. I have four different torani flavors right now, all of which would make a good soda either alone or in combinations. I made a run to the grocery store a half-hour ago for other misc. needed items and they had Schweppes stuffs on sale, so I figured it would be a good time to experiment. I had one problem though: carbonated waters. There are apparently three types of unflavored carbonated water: seltzer, tonic, and club soda. I have no idea which is generally used to make italian soda.

It was on sale, so I bought a small bottle of each to experiment with. I’m about to google to discover the real answer. But in the meantime, which would you use? And what is your understanding of the purpose of each of these carbonated waters?