What is green house effect and global warming??

The greenhouse effect is the conjecture that the surface temperature of a planet is significantly affected by the presence of certain trace gases in its atmosphere, notably water vapor and carbon dioxide. The absorption spectra of these shows major absorption bands at long wavelength infra-red but only minor bands in short wavelength infra-red.

The argument is that increasing the density of trace gases will increase the temperature of the surface. The suggestion is that that radiation coming from the planet's surface which, in the absence of an atmosphere or of trace gases, would radiate out into space is instead absorbed by those gases. Therefore the temperature of the surface and the atmosphere is bound to be higher than it would be were the trace gases absent.

Quantifying the effect on Earth is a very challenging task, whether done by attempting to model the thermodynamics of the atmosphere or by experimental measurement.

The greenhouse effect*has nothing to do with how greenhouses work. Greenhouses work by trapping a volume of air stationary over a sunny surface, so that the temperature rises significantly more than it would if the air was allowed to disperse.

Global warming usually refers to the estimated temperature rise globally since the end of the last Little Ice Age (about one Celsius degree per century). Sometimes the term is used to refer to a conjectured part of that which could be attributed to human activity. The term became unfashionable when global temperatures did not rise during the first two decades of the twenty-first century, and was in some circles replaced by the term climate change. An attempt to further change it to climate disruption has not had much impact.