Certain mushrooms, a type of fungi, are poisonous. The ones in the store and on pizzas are safe because they are farmed. The stores that sell them know what kind they are and that they are safe to eat. An example of a mushroom that is dangerous is the death cap mushroom, and it can kill you. Most people can't tell the difference between safe and unsafe mushrooms, so poisonings happen when wild mushrooms are picked and eaten.
Mushrooms belong to a special group of fungi called club fungi.
The name comes from the club-shaped structure that produces the spore. The umbrella-shaped part of the mushroom is the mushroom's cap. The cap is part of the mushroom's fruiting body. It contains spores. The cap can be any color, depending on the species of mushroom.