Why is drinking water important ?

I always think i am dehydrated because i don't drink enough water in a day. I don't know if its my body mechanism or something but i can go whole day with just a glass of water and it doesn't effect my productivity. But u wanted to keep myself hydrated but first i wanted to why water is so important for our body and what is the purpose of it.
I always think i am dehydrated because i don't drink enough water in a day. I don't know if its my body mechanism or something but i can go whole day with just a glass of water and it doesn't effect my productivity. But u wanted to keep myself hydrated but first i wanted to why water is so important for our body and what is the purpose of it.