What is the ozone layer? Why do we need it?

Ozone is a polymer of oxygen which has three atoms of oxygen in its molecule, instead of the normal two found in ordinary oxygen. Ozone aculates in the upper reaches of the earth's atmosphere, perhaps as a result of the action of the sun's UV radiation which splits the molecule into atoms, but these atoms somehow recombine to form not di-atomic(O2) oxygen, but tri-atomic (O3) ozone. Nature, it appears, has a good reason for enabling the formation of this process. The ozone layers above the earth's atmosphere are known to act as shields against dangerous cosmic radiations to which all planetary objects, including the earth, are exposed. As always, man seems to be his own worst enemy. Pollutants produced from certain refrigeration machines, known as CFCs (Carbon floro-chlorides) are particularly corrosive to the ozone layer, being capable of punching holes in or eating away whole portions of this protective shield. This is known as Ozone layer depletion and has been most noticeable in the atmosphere over the Antartica.