Ozone depletion describes two distinct but related phenomena observed since the late 1970s: a steady decline of about 4% per decade in the total volume of ozone in earth's stratosphere (the ozone layer], and a much larger springtime decrease in stratospheric ozone over Earth's polar regions. The latter phenomenon is referred to as the ozone hole. In addition to these well-known stratospheric phenomena, there are also springtime polar tropospheric ozone depletion event.The details of polar ozone hole formation differ from that of mid-latitude thinning but the most important process in both is catalyic destruction of ozone by atomic halogens .

that s all I know about ozone.........
It is a harmful layer of oxygen bot when o2 is broken into o atoms by uv rays.It forms o3
due to pollution holes are formed and they allow uv rays to reach on earth