Hey, what's wrong with spring water?
I admit to occasionally buying a couple jugs of spring water for my lighter beers, rather than hoping the Campden tablet did its job. I like the clean, non-chlorinated base that spring water provides, without having to worry about adding in a bunch of minerals (as in distilled or RO water).
Its a meaningless term. Some folks use it to mean bottled water from Walmart which is probably RO from a municipal source.
Others use it to mean I buy x gallons of y brand of water.
What's its mineral content?
Is it on the bottle?
Is it suited to brewing?
Is it suited to that style of beer?
If your going to invest and spend orders of magnitude more money on store bought water over tap water you probably want to know its mineral content precisely.
Are Perrier, Fugi, Avian spring waters? Are they suited to brewing? Yes to the former and I have no idea to the latter, never looked at the minerals.
It is simply a meaningless term that requires explanation regarding the mineral content and why this is suitable for brewing.
RO water is a simple term, you know what your getting
Distilled water the same. "It does exactly what it says on the tin".
Spring water, no clue what someone means. It's as specific as tap water