The stratosphere is the layer of the Earth's atmosphere that exists above the troposphere. On average, the bottom of the stratosphere is at a height of about 12 km and the top of the stratosphere (called the stratopause) is around 50 km. The layer above the stratosphere is the mesosphere.
Temperature increases with height in the stratosphere. This causes the stratosphere to be buoyantly stable, which suppresses vertical motions.
The ozone layer is in the upper part of the stratosphere.