The multilayered gaseous envelope above the earth surface is called atmosphere. It contains nitrogen, oxygen, carbon dioxide, helium, hydrogen, ozone etc.
It is the thin layer of air that surrounds the earth and is made of various gases. The gravitational force of the earth holds the atmosphere around it. If there was no atmosphere, life would not have been possible on earth because the atmosphere contains the air we breathe, protects us from the radiation of sun, keeps the climate on Earth moderate, etc.