As you may know the earth’s atmosphere is made up of various gases (mainly nitrogen and oxygen) which reach to outer space. The gases are held to the earth by gravity.
You may also know that the atmosphere is layered. They are in ascending order:
Troposphere – from the ground to about 17 km at the equator (about 7 km at the poles).
Stratosphere – rises to 50 km
Mesosphere – to 80 km
Thermosphere – to 800km
(The Karman Line at about 100km designates outer space_
However there are smaller layers between these. The Tropopause is a layer about 12km wide at the top of the troposphere. The significance of these are the characteristic of constant temperature. As you probably know the atmosphere cools as you go up in the troposphere. Then in the stratosphere the atmosphere increases in temperature. The pauses are simply small layers of relatively constant temperature between the layers.