A mushroom is a type of fungus that typically has a cap, stem, and gills. They can be found in various environments, including forests, grasslands, and even urban areas. Mushrooms play a crucial role in ecosystems by breaking down organic matter and recycling nutrients back into the soil. There are thousands of mushroom species, some of which are edible, while others are toxic. Common edible varieties include button mushrooms, shiitake, and portobello. Mushrooms are also used in cooking for their unique flavors and textures, making them popular in many cuisines around the world.