What is ozone and why is it useful to the earth

Ozone is the protective layer of gas in the atmosphere, which prevents most of the harmful radiations coming from Sun to enter the earth's surface. It mostly reflects shields earth from ultraviolent radiation, an excess of which can be hazardous for earth. Plants cannot live and grow in heavy ultraviolet radiation, nor can the plankton that serve as food for most of the ocean life. The ozone layer acts as a shield to absorb the UV rays, and keep them from doing damage at the Earth's surface. Thus, this layer is very useful to living organisms on earth and for their survival