What is greenhouse effect? The rise in the atmospheric temperature caused by greenhouse gases allowing incoming solar radiation to pass through the earth atmosphere and preventing outgoing radiation from surface or lower atmosphere to escape in the space.  It contributes to around 60 degrees Fahrenheit more than the normal for sustainability on earths life and counterbalancing energy.

You can find lots of definition in the internet for greenhouse effect and all of them are pointing into the same principle with some broader explanation on the subject.  As an excerpt like the effect of greenhouse gases in the atmosphere or warming of the atmosphere by trapping the long wave radiation being radiated to space.