In fact, it's nothing you can see.
Ozone is a naturally occuring gas found on the earth's atmosphere.
At the outer edge of the atmosphere there is a thin layer of ozone gas that is critical to life on earth. It is the stratospheric ozone layer. This layer protects us from the harmful rays of the sun. If it weren't for the ozone layer, we'd get wicked sunburn, wreck our eyes, and kill our plants. When certain chemicals used on earth escape into the atmosphere they are broken down by solar radiation and release chlorine and bromine atoms which, in a chainreaction, destroy ozone molecules.