Ozone in the stratosphere (that region about 10 miles above our heads) protects us from incoming ultraviolet radiation (that radiation which causes sunburns).
Here you can see how ozone is distributed around the world. Ozone varies naturally over the earth. It also varies naturally from season to season. On this day you can see the ozone hole over Antartica. Is there a hole over the Artic? What are the levels over Iowa?
Shown above is the ozone hole as seen from satellite instruments. CFCs emitted into the atmosphere cause the ozone hole. You can see that the ozone hole changes with each month. In which month does the hole first appear? What happens to the hole?