Water is a chemical compound, with composition H2O, one oxygen and two hydrogen atoms connected by covalent bonds. Under standard temperature and pressure conditions, it is a liquid, but can be easily found in its solid state (ice) or gaseous (water vapor, or steam) in case of temperature, respectively, below 3.98 °C (39.16 °F) or approaching 100 °C (212 °F).
Water is the major constituent of the fluids of all known forms of life, and is vital for each of them.
Water from a natural spring and containing minerals is called mineral water. If containing gases too, it is considered effervescent. In older times, mineral waters were usually used (or consumed) at their spring sources. Nowaday, they are usually bottled at the source and then commercialized. Of course, water needs to be potable in order for humans to safely consume it without risk.
Since antiquity, but available to very few people until the second half of the 19th century, in developed contries indoor plumbing has spread. Tap (or running) water is usually assumed to be potable, and usually it actually is. In case of doubt, a few water purification methods can be used, like boiloing or water filters.
In cooking, water is an essential ingredient, both to make lots of recipes, and to cook food like pasta, a staple food here in Italian gastronomic tradition.