Also known as: Portobello mushroom, Common mushroom, Champignon mushroom, Chestnut mushroom
Most of the mushrooms sold in supermarkets in the US are cultivated forms of the button mushroom. The white variants are sold as "button mushrooms", the brown as "cremini" or "baby bellas", and full-grown caps as "portobellas." They occur quite infrequently in the wild, in grassy fields around the Northern Hemisphere.