The sky is a part of the outer surface of the surface. There are two parts to the sky. The atmosphere and space are also called astronomers in astronomy. From the surface the sky is imagined as a sphere in which the sun, moon, stars and planets travel. The B-sphere is usually divided into several constellations. The word sky is used to indicate any point above the surface.
In the case of weather, the sky is simply the thickest part of the lower part of the atmosphere.
The sky looks blue for the scattering of light in daylight. At night the sky looks like a black carpet. During the day, the sun can be seen in the sky. And the moon and planets can be seen in the night sky.
The sky looks blue because of the scattering of light. When a light falls on a particle, it spreads the light in different directions, called light scattering. The lower the wavelength of the light, the higher the radiation of that light. Light scattering is proportional to the quadrilateral of its wavelength. The wavelengths of blue light are the lowest, so the diffusion of light in the sky is higher. And the sky looks blue. The molecules in the cloud are quite large and therefore distract the light other than blue. As a result, the color of the cloud is much white.