Amanita muscaria (fly agaric).JPG
The toxic mushroom  Amanita muscaria , commonly known as “fly agaric”
 Scientific classification 

mushroom or toadstool is the fleshy,  spore -bearing  fruiting body  of a  fungus , typically produced above ground, on soil, or on its  food  source.

The standard for the name “mushroom” is the cultivated white button mushroom,  Agaricus bisporus ; hence the word “mushroom” is most often applied to those fungi ( Basidiomycota ,  Agaricomycetes ) that have a stem ( stipe ), a cap ( pileus ), and gills (lamellae, sing.  lamella ) on the underside of the cap. “Mushroom” also describes a variety of other gilled fungi, with or without stems, therefore the term is used to describe the fleshy fruiting bodies of some  Ascomycota . These gills produce microscopic spores that help the fungus spread across the ground or its occupant surface.

Forms deviating from the standard  morphology  usually have more specific names, such as ” bolete “, ” puffball “, ” stinkhorn “, and ” morel “, and gilled mushrooms themselves are often called ” agarics ” in reference to their similarity to  Agaricus  or their order  Agaricales . By extension, the term “mushroom” can also refer to either the entire fungus when in culture, the  thallus  (called a  mycelium ) of species forming the fruiting bodies called mushrooms, or the species itself.