Cloud is a visible polymer floating in the air, which is condensed by small water droplets or small ice crystals liquefied by water vapor in the atmosphere when it is cold.
Clouds are the tangible result of the huge water cycle on the earth. The sun shines on the surface of the earth, and water evaporates to form water vapor. Once the water vapor is supersaturated, water molecules will gather around the dust (condensation nucleus) in the air, and the generated water droplets or ice crystals will scatter sunlight in all directions, thus creating the appearance of clouds.
Moreover, clouds can form various shapes, and they are divided into many kinds because of their different heights and shapes in the sky.