The gases which absorb radiations of thermal range and emits them in atmosphere.. Reabsorb radiations again and again emit.. Green house gas don't let go radiations out of the atmosphere
.. Examples are - Co2 , CH4, CFC, N20
They are responsible for Earth's average temperature 15 degree celsius
if there is no greenhouse effect the average atmosphere of earth is - 18°C.
due to human activities like deforestation, burning of plastic and fuels , using a refrigerators extra amount of greenhouse gases are added in the environment causing global warming.