Ozone occurs naturally in a layer of the atmosphere called the stratosphere. The ozone hole is a region of the stratosphere over Antarctica (and to a lesser degree over the Arctic) where the amount of ozone had decreased in the late 20th century, due to chemical reactions between ozone and human-made substances from things like aerosol spray cans and refrigerants. Ozone is the molecule 03 whereas oxygen is the molecule 02. Humans breath oxygen, but ozone leads to health hazards since it behaves like oxygen, but is significantly heavier than oxygen.
How is ozone different from oxygen?