There are many confusing statements about water and testing. At this point, you are only interested in finding out what the plain water you are using for brewing has as far as mineral content is concerned. ALL those other measurements have to do with the brewing process, and you should ignore all that for now.
The basic testing needed is usually done by a lab. In the US, Ward Labs does it for about $42.
You want to know the concentrations of these minerals at least:
Calcium
Magnesium
Sodium
Iron if possible (Iron is bad for beer, so 'none' is best)
Chloride (Not chlorine, but the chlorine ion, which is called Chloride)
Sulfate (Again, not Sulphur, but the ion Sulfate, SO4)
Bicarbonate (HCO3)
It is also useful to know the pH and 'Total Alkalinity' and 'Hardness' (Both as CaCO3) but these are not essential.
All of these minerals have some effect on brewing results, but some more than others. Calcium, Chloride and Sulfate (and especially the ratio of these last two) are arguably the most important.
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All that being said, you can completely bypass this question by buying distilled or Reverse Osmosis (RO) water. Aldi sells distilled water here in the US for about 80 cents a gallon; most grocery stores or pharmacies sell distilled water. This kind of water has zero* minerals, and is a good starting point if you want to add minerals precisely. I recommend it highly, but then you will need to buy some Calcium Chloride and perhaps some Calcium Sulfate so you can add minerals. You should have at least 50 ppm of Calcium in your water for good fermentation. If you use extract (liquid or dry) it will have all the minerals you need.
Others will chime in on this, but I suggest reading
this on brewers friend to learn more. You might find a water test profile already from your water supply posted
here.