State one important function of ozone layer in the atmosphere

State one important function of ozone layer in the atmosphere. How is it formed there ? Which compounds are responsible for the depletion of ozone layer ? How do these compounds enter into the atmosphere ?

Ozone present in the upper regions of the atmosphere protects us from dangerous UV radiations.
Formation of ozone layer:
Ozone at the higher levels of the atomosphere is a product of UV radiation acting on oxygen molecule. The higher energy UV radiations split apart some molecular oxygen into free oxygen (O) atoms. These atoms then combine with the molecular oxygen to from ozone as shown:
${{O}_{2}}$----------> O+ O
Oxygen and single oxygen combines to form ozone.
Chlorofluorocarbons (CFCs) are responsible for the depletion of ozone layer. These compounds enter the atmosphere through sprays, aerosols, refrigerators, air conditioners, etc., which use CFCs.