If there was no cloud in the sky, then this world would not have been in existence. Me and you would not have been there. There is no rain, no heat, no cold. So not so beautiful nature.
Clouds contribute a lot in nature. Nothing happens if there is no cloud.
They are the main cause of rain and source of water on our earth. If there were no clouds, there would have been no rain nor there would have been any water worth living on this earth.
Clouds are made of water vapor or snowflakes.
Ever wandered, when water evaporates from the water sources present on the earth, the water evaporates and goes into the sky where it takes a visible amount of what we call a cloud. When these clouds hit a high mountain, they come back to the earth in the form of rain.