Why does increasing the amount a greenhouse gas increase the temperature of a planet?

Greenhouse gass effects the increase of temperatures on Earth, which means plant temperature rises as well. the reason for the rise in temp. is due to the fact that the gass acts as a wall that doesn't allow heat to go through. So when greenhouse gass is applied to a plant the gas doesn't let the heat go through therefore raising the temperature.

Green houses gases like CO2, water vapour and methane, these gases traps heat in its structure, this is same like glass house in which infrared waves can only enter but after entering the waves will become polarisezed it will prevent waves going out and hence increrasing the temperature