Degassing is the releasing of gases from roasted coffee. Roasting coffee causes gas (carbon dioxide and more) to form inside the bean. The first few days after roasting, these gases begin to leave the coffee beans. There are a few misconceptions about the purpose of letting coffee degas.
The main benefit is to prevent any negative effects when brewing-mainly an uneven extraction. Degassing coffee prevents air pockets from forming when brewing coffee that could negatively impact the taste.