All plants need water. Desert plants store as much water as they can inside their bodies, to be used as they need it. That is why cactus arms and pads are so thick. Cactus guards its water with spikes to prevent people or animals from taking it. Animals and birds drink water and, in a broad way, so do plants.
People use water in many ways.
We travel on water, use it in our businesses, fish and play in it, cook and keep cool with it, clean our homes, dishes, clothes and even our bodies with it. We use it to drive some engines, and to cool most engines and nuclear power plants. We use it to clean microchips, carry away our wastes, create power as it flows through turbines at dams, water our landscaping, fight fires and create beautiful water art in fountains. We humans use water in so many different ways that our civilization would not exist if we did not have water. Without a swamp cooler or air conditioner in the summer, you would be very uncomfortable, but you can help your body a lot in that heat by drinking more water.