The greenhouse effect refers to the way the sun's heat radiates up from the warmed surface of the earth, where it is absorbed by the greenhouse gases in the atmosphere. The more gases there are, the more heat is absorbed.
The natural greenhouse effect is supported by the water and carbon cycles. This has kept the earth warm enough for life for millions of years.
The accelerated greenhouse effect is now being caused by extra greenhouse gases that the carbon cycle can not deal with. This is causing global warming.
The greenhouse effect is a natural process, whereby the earth's atmosphere traps some of the heat from the sun (mostly by methane and carbon dioxide gasses), warming the earth. Without it, the earth would be unable to support life.
Human activities like burning fossil fuels, deforestation, and methane from landfill sites and rice paddies are artificially increasing the effect, warming the earth unnaturally