It’s all two parts hydrogen, one part oxygen, but water ends up having some pretty different properties depending on where exactly on the planet it’s been drawn from, and how it ultimately gets to you.
Natural mineral water
The main characteristic of natural mineral water are the trace minerals and mineral salts that it contains. It must be obtained directly from underground sources protected from pollution risks, and which are highly regulated (in some countries, these sources must undergo 2 years of frequent testing for microbes in order to be certified). Natural mineral water must also be packaged close to its source, and cannot be subjected to most treatments, except for carbonation, or removal of iron and/or magnesium.
Spring water refers to water collected directly from an underground spring that rises to the surface. Because it’s taken straight from its source, spring water has not passed through municipal water treatment and distribution systems. It must still meet health and safety standards, and is not subject to any modification other than those permitted by these standards.
What we’ll call “prepared water” refers to water drawn from municipal water supplies (in developed areas, with systems of distribution for clean, safe drinking water). Prepared water is usually drawn from large reservoirs, lakes, rivers, or aquifers, and then treated in order to ensure compliance with chemical, microbial, and other safety standards. Contrary to popular many popular assumptions, “tap water” is not always of a lower standard than bottled water, and depending on the exact bottled water in question, may even be cleaner.