How do you understand the term “greenhouse effect”?

As a result of human activity, an excess amount of carbon dioxide, methane and halogenated alkanes appears in the earth’s atmosphere, which leads to the creation of an umbrella layer like a BE, which serves as a screen and creates a greenhouse effect. This leads to a slight increase in the temperature of the planet, which, in turn, causes the ice at the poles of the earth to melt, rise in the level of the oceans and flood some countries.