From Encyc

Water is a compound made from two hydrogen and one oxygen, with the formula H2O. It is very common on the surface of the Earth, forming large oceans and clouds in the sky, and composing a significant portion of the bodies of most organisms.

Water is a good solvent and useful when cleaning things. It can also be put into water pistols and water balloons, and used to soak one's friends.

It is also important for humans to drink a large amount of water.