The Ozone layer or ozone shield is a region of Earth's stratosphere. It contains high concentrations of ozone gas (O3) in relation to other parts of the atmosphere. The main function of the ozone layer is to filter the Sun's ultraviolet radiation (UV-B), thereby protecting the Earth from its harmful effects and also plays a key role in regulating the temperature of the Earth's atmosphere, without which it would've been difficult for life forms to survive.