Clouds are a type of meteorological phenomenon that consists of a visible mass of condensed water droplets or ice crystals suspended in the atmosphere above the surface of the Earth. They are formed when air containing moisture rises and cools to its dew point, forming tiny water droplets or ice crystals. Depending on their altitude, clouds can be classified into several types, including cirrus, cumulus, stratus, and nimbus. Clouds play an important role in the Earth's climate system by reflecting sunlight and trapping heat near the surface of the planet.