Air is mostly gas. It's a mixture of different gases. The air in Earth's atmosphere is made up of approximately 78 per cent nitrogen and 21 per cent oxygen. Air also has small amounts of lots of other gases, such as carbon dioxide, neon, and hydrogen. Air is pulled into the body by lungs and used to fill tiny air sacs that allow blood cells to pick up oxygen, which is then distributed across the body's cells. Through the process of cellular respiration, this oxygen can then be used to break down sugars and create energy.
The atmosphere of Earth is the layer of gases, commonly known as air, retained by Earth's gravity, surrounding the planet Earth and forming its planetary atmosphere. It provides oxygen for humans and animals to breathe and carbon dioxide for plants. Through the hydrological (precipitation) cycle, plants and animals receive the water they need to survive. There are atmospheric layers moving upward from ground level, the layers have named the troposphere, stratosphere, mesosphere, thermosphere and exosphere. The exosphere gradually fades away into the realm of interplanetary space.