The major function of the ozone layer is to stop the harmful radiations coming from the sun as well as from stars.
Ozone captures those radiations which are of low wavelength. It also stops the harmful ultraviolet rays. These radiations are very harmful for living beings. If these radiations will reach the earth directly then most of the living beings will have to suffer with skin problems.
Those radiations which have the wavelength range less than that of 3000 Armstrong are absorbed mostly by ozone layer.