Mushrooms are the fruiting body offungi, which feed primarily on decomposing plant material, aided by their ability to produce cellulose. The body of the fungus is called mycelium and its individual parts are microscopic. Since the fungus is usually dispersed over a relatively large underground area it is rarely noticed. In nature some species of fungus may have a body that spreads over hundreds of square miles. Because mushrooms are fungi, they are usually placed in a Kingdom of their own apart from plants and animals. Mushrooms contain no chlorophyll and most are considered sacrophytes. That is, they obtain their nutrition from metabolizing non living organic matter. This means they break down and "eat" dead plants.
The mycelium stores nutrients and other essential compounds, and when enough material is stored and the conditions are right they start to fruit - produce mushrooms.
There are many species of mushroom. Some are edible and are widely used for their distinctive flavor in various cuisines, especially European and Oriental foods. Other mushrooms can be poisonous to varying degrees, and some contain powerful mind-bending drugs. For this reason, it is unwise to eat wild mushrooms without a definite knowledge of their species. There are no reliable general rules for identifying dangerous mushrooms, they must be positively identified.