The Ozone Layer
This is simply a layer in the stratosphere containing a relatively high concentration of ozone.
The earth's atmosphere is divided into several layers, and each layer plays an important role. The first region extending about 10km upwards from the earth's surface is called the troposphere. Many human activities like mountain climbing, gas balloons and smaller aircrafts operate within this region.
The next layer, extending about 15-60 km is called the stratosphere. The ozone layer is mainly found in the lower portion of the stratosphere from approximately 20 to 30 kilometres (12 to 19 mi) above earth, though the thickness varies seasonally and geographically.
The ozone layer protects the earth from the suns UV Rays. If the ozone layer is depleted by human action, the effects on the planet could be catastrophic.