Clouds are formed as a result of saturation of the air when it is cooled to its dew point, or when it gains sufficient moisture (usually in the form of water vapour) from an adjacent source to raise the dew point to the ambient temperature. They are seen in the Earth’s homosphere (which includes the troposphere, stratosphere, and mesosphere).
Source: Wikipedia
In Photography, cloudy landscape, also called “cloudscape” give more depth and sometimes abstract shapes and colour gradients.