Crimini mushrooms, or Agaricus bisporus, are immature portobello mushrooms. They are brown and known under a variety of other names, like swiss brown, roman brown, italian brown and chestnut.
Mushrooms are the fleshy fruiting body of a fungus. They grow above ground, soil or from a food source. UV ray-treated (due to both sunlight and articial UV light tech) mushrooms are a source of vitamin d2. Many mushrooms are poisonous, resembling certain edible species. Gathering mushrooms in the wild is risky for the inexperienced and should only be undertaken by persons knowledgeable in mushroom identification.