Lingzhi is a polypore mushroom that is soft (when fresh), corky, and flat, with a conspicuous red-varnished, kidney-shaped cap and, depending on specimen age, white to dull brown pores underneath.It lacks gills on its underside and releases its spores through fine pores, leading to its morphological classification as a polypore.

Ganoderma lucidum generally occurs in two growth forms, one, found in North America, is sessile and rather large with only a small or no stalk, while the other is smaller and has a long, narrow stalk, and is found mainly in the tropics. However, many growth forms exist that are intermediate to the two types, or even exhibit very unusual morphologies, raising the possibility that they are separate species. Environmental conditions also play a substantial role in the different morphological characteristics lingzhi can exhibit. For example, elevated carbon dioxide levels result in stem elongation in lingzhi. Other forms show "antlers', without a cap and these may be affected by carbon dioxide levels as well.

Reishi is mostly a medicinal mushroom. Reishi is used as a daily tonic to maintain and improve good health, increasing longevity, in the treatment of cancer and resistance to and recovery from diseases.

Due to its bitter taste, Lingzhi is traditionally prepared as a hot water extract. Thinly sliced or pulverized lingzhi (either fresh or dried) is added to a pot of boiling water, the water is then brought to a simmer, and the pot is covered; the lingzhi is then simmered for two hours. The resulting liquid is fairly bitter in taste, with the more active red lingzhi more bitter than the black. The process is sometimes repeated. Alternatively, it can be used as an ingredient in a formula decoction or used to make an extract (in liquid, capsule, or powder form). The more active red forms of lingzhi are far too bitter to be consumed in a soup.

It is rarely found in nature, and has been used as a herbal medicine for more than 4,000 years in traditional Chinese medicine, making it the oldest mushroom known to have been used in medicine.

Lingzhi is the Chinese name (or Japanese: 'Reishi') for one form of the mushroom Ganoderma Lucidum. 'Lingzhi', in Chinese, means "herb of spiritual potency", and because of its multiple health benefits and absence of side-effects, it has attained an unparalleled reputation in the East as the ultimate herbal substance. It is said that for thousands of years, lingzhi was the most sought-after herb by mountain sages and emperors and empresses of China and Japan. Lingzhi has now been added to the American Herbal Pharmacopoeia and Therapeutic Compendium.

In nature, Lingzhi grows at the base and stumps of deciduous trees, especially maple (National Audubon Society; Field guide to Mushrooms,1993). Only two or three out of 10,000 such aged trees will have Lingzhi growth, and therefore its wild form is generally rare.

Lingzhi is nowadays effectively cultivated and sold in many Asian markets. Western health shops often stock extracts of Ganoderma Lucidum, labeled as 'lingzhi'; however, they sometimes belong to another type of the same family of mushroom, which do not have the full range of medicinal effects.