Earth's atmosphere is a layer of gases surrounding the planet, held in place by gravity. It is essential for life, providing the air we breathe and protecting us from harmful solar radiation. The atmosphere is composed mainly of nitrogen (about 78%) and oxygen (about 21%), with trace amounts of other gases like carbon dioxide and argon. The atmosphere is divided into several layers, including the troposphere, where weather occurs, and the stratosphere, which contains the ozone layer that absorbs ultraviolet radiation. These layers play a crucial role in regulating temperature and climate, making Earth a suitable habitat for living organisms.