A
mushroom 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, just as do store-bought white mushrooms.
"Mushroom" describes a variety of gilled fungi, with or without stems, and the term is used even more generally, to describe both the fleshy fruiting bodies of some
Ascomycota and the woody or leathery fruiting bodies of some
Basidiomycota, depending upon the context of the word.
Forms deviating from the standard
morphology usually have more specific names, such as "
puffball", "
stinkhorn", and "
morel", and gilled mushrooms themselves are often called "
agarics" in reference to their similarity to
Agaricus or their place
Agaricales. By extension, the term "mushroom" can also designate the entire fungus when in culture or the
thallus (called a
mycelium) of species forming the fruiting bodies called mushrooms, or the species itself.
Source: http://en.wikipedia.org/wiki/Mushroom