The Earth's atmosphere is a mixture of gases. The most abundant gas in the atmosphere is nitrogen 78% with oxygen the 2nd most abundant at 28%.
Troposphere- (lowest layer) this is where we live and weather occurs, temperature decreases.
Stratosphere- temperature increases, this layer contains the ozone layer. Ozone is three atoms of oxygen combined and the ozone protects from UV radiation.
Mesosphere- temperature decreases, meteors burn up in this layer.
Thermosphere- temperature increases, beginning of outerspace.
Pauses- these are the boundaries between layers of the atmosphere, see diagram.