The document discusses the layers of the Earth's atmosphere. It is divided into 4 layers - the troposphere closest to the surface from 0-10 km, the stratosphere from 10-25 km containing the ozone layer, the mesosphere from 25-100 km, and the thermosphere the highest layer from 100-400 km where meteorites burn up. The atmosphere contains nitrogen, oxygen, argon, carbon dioxide and other gases, with nitrogen being the most abundant.