Atmosphere refers to a layer of gasses that encapsulate the Earth and contribute to the sustenance of life on our planet. When we look up at the stars at night and they appear to twinkle, it is because we are looking at them through the layers.
The further away objects are from the viewer the lighter and “fuzzier” they may appear. This is because the human eye’s ability to make out contrast diminishes over a distance. Objects that are close will be more clearly delineated and distinct from their background.