If your glass has stains we would call it hard water stains, but usually its more than just that:

hard water stains and spots,

acid rain spots,

calcium deposits,

lime,

scale,

silicone buildup,

tar,

road grime,

soap scum, and more.

Hard water is water that contains dissolved
hardness minerals above 1 GPG.
What are hardness minerals?
Calcium, manganese and magnesium are the most common, the fine particles lift off the white mineral deposits.
"Hard" Water a definition:
Water than contains dissolved minerals is called hard water. Water containing low percentages of calcium and magnesium, carbonates, bicarbonates, sulfates, or chlorides, as a result of long contact with rocky substrates and soils. Degree of hardness is expressed either as grams per gallon or parts per million (ppm) of calcium carbonate (1 grain of CaCO3 per gallon is equivalent to 17.1 ppm). Up to 5 grains is considered soft, over 30 grains is very hard. Hardness may be temporary (carbonates and bicarbonates) or permanent (sulfates, chlorides).
Typically "hard" water makes itself known by these characteristics:
1. Soaps do not foam as much
2. A residue is left behind when the water evaporates
3. Polished surfaces tend to dull
4. Surfaces tend to get discolored
Myth - Any cleaner will do.
RUB OUT Is Seven Chemicals Formulated to Remove Hard Water, Alkali and Aluminum Screen Stains from glass.
The RUB OUT powder easily dissolves on a wet non-abrasive pad. Removes surface stains using a circular motion.
RUB OUT does not contain harsh hydrofluoric or hydrochloric acid.
Recommended for professional use only.