A greenhouse gases are gases that absorb long-wavelength infrared radiations and prevent them from escaping back into the atmosphere, thereby keeping the earth warm.
Without greenhouse gases, life would not have existed on the earth as the temperature of the earth would have been extremely low.
However, an increased number of industries, and automobiles are leading to an increased emission of greenhouse gases nowadays.
Carbon dioxide, methane, chlorofluorocarbons, and nitrous oxides are called greenhouse gases.