Although you may have learned that pure water is H2O, water for brewing must contain much more. Not only do dissolved minerals and ions affect the taste of ingredients in beer, they also provide necessary nutrients for growing yeast and buffering reactions relating to the pH of the water and the grains. Common dissolved minerals found in brewing water include:
Water from different sources around the world have different concentrations of these minerals that are naturally dissolved in it. The water found in Burton, England has a different profile from the water found in Pilsen, Czech Republic. These differences in water is what partially led to different styles of beer. Pilsner beer became possible due to the extremely soft water found in Pilsen, while the sulfate content in the water around Burton favored hoppy beers that became what we know as Pale Ale.