As defined by Wikipedia, "it is a transparent, tasteless, odorless, and nearly colorless chemical substance, and it is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a solvent)."
In layman's terms, water is a clear liquid that you can find in a lot of places; the ocean, your sink, in water bottles, in your own body. It should be considered a human right, as it is vital to almost every living creature's survival.
To be frank, if you don't have at least a little bit of water, you would die. On a far less morbid note, there are a lot of benefits to having a lot of water, which includes:
and most importantly... it's just really nice.