Plants need water the same way that we humans do. Much of their structure contains water and they use it along with minerals and sunlight to produce energy to grow. Plants have evolved in their natural environments to utilise water both in its liquid form, as rain, and as a gas in the form of vapour or humidity in the air, so where a plant comes from dictates what kind of moisture levels it needs. In the home environment, plants are completely dependent on you to give them the precious H2O that they require to flourish.
More than any other