Club soda vs seltzer vs mineral water
There are several types of carbonated water used behind the bar.
Seltzer or soda water - Plain, unflavored water that has been carbonated by the producer.
Club soda or sparkling water - Water with added mineral salts (bicarbonates and/or citrates) that has been carbonated by the producer. The salts give the soda a little acidity and mouthfeel though this is subtle.
Mineral water - Water that has natural minerals in it either naturally or artificially carbonated.
I generally specify club soda in the drink recipes on this site. If a different form of carbonated water is necessary for the recipe it will be specified.
I find there to be little difference between these three types of carbonated water in drinks that have a sweetener. The differences between these waters become more pronounced in drinks with little or no sweetener (such as a Rickey). Here a mineral water can show through and as such is a good choice.
Homemade club soda
You can get a soda siphon to make your own seltzer (or with the addition of a little mineral salts, club soda). I used to use one but have become disappointed with it. Soda siphons have a safety valve that let's off excess CO2 to prevent bottle explosions. This sounds like a good thing, but the valve is set at a rather low pressure so that when you charge the bottle, some of the CO2 that you paid good money for goes right out the valve.
So your soda is fizzy, but not very. Nothing like a commercial soda system. One thing I think craft cocktail bars need is a commercial soda system. They try to go old fashioned and use the big siphons but these siphons have been designed by lawyers with the safety valves. They are nothing like the vintage siphons that would really get some pressure for super fizzy soda.
At home you are kind of screwed. There are soda systems you can buy but I just don't trust that they'll develop enough pressure. You can get a small CO2 tank, a regulator, and some stoppers to make some higher pressure soda (the regulator will control the pressure). I will probably go this route in the future.
But for now it's store bought club soda and mineral water on occasion. If you have a soda system that works for you let us know in the comments below.