Most of the earth's atmosphere consists of a mixture of only a few gases - nitrogen, oxygen and argon; these three gases together make up more than 99.5 % of all gas molecules in atmosphere . These gases, which are the most abundant in the atmosphere,  they show almost no effect on the warming of the Earth and its atmosphere because they do not absorb visible neither infrared radiation . However, there are smaller gases that make up only a small fraction of the atmosphere (about 0.43 % of all air molecules, most of which is water vapor with 0.39 %) that absorb infrared radiation. These "trace" gases contribute substantially to the warming of the Earth's surface and atmosphere due to their ability to trap infrared radiation emitted by the Earth (see below for details on the greenhouse effect). Since these trace gases affect the Earth in a somewhat greenhouse-like manner, they are referred to as greenhouse gases or greenhouse gases. (More on gml.noaa.gov)