Simplify the following text for a Grade 9 native English-speaking person.
Original: The greenhouse effect is caused by greenhouse gases ; the most important greenhouse gasses in Earth 's atmosphere are : water vapor , carbon dioxide , and methane .
Simplified: The greenhouse effect heats the earth because greenhouse gases absorb outgoing radiative energy and re-emit some of it back towards earth . A greenhouse is built of any material that passes sunlight , usually glass , or plastic .