Portobello is a type of mushroom, specifically an edible fungus belonging to the genus Amanita. It has a cap that can grow up to 15 cm in diameter and comes in various colors such as brown, gray or black with a white ring around the edge. The portobello mushroom is a large, meaty variety of the common button mushroom (Agaricus bisporus). They are often used as a vegetarian substitute for meat due to their hearty texture and savory flavor.