The truffle is the aromatic fruit of an underground fungus. It develops in the roots of certain host trees in a symbiotic relationship. The tree's roots and fungus bond in a process called mycorrhization. The mycorrhizas look like small baseball bats and generally form in clumps. The truffle provides mineral salts (phosphorus) for the tree. It helps the tree to support high calcium levels to obtain its nutrients and it is a great source of moisture.

A variety of oaks, hazels, some pine species, willows, poplars and firs can host truffles. Different truffles do better with different types of trees. Tuber melanosporum, the valuable black truffle, is commercially grown with certain oak species and hazels.

There are many different kinds of edible truffle, some rarer and some more valuable than others. The most valuable truffle is the Italian white truffle (Tuber magnatum), which is not yet commercially grown, followed by the black or Perigord truffle (Tuber melanosporum), which is commercially grown in France, Chile, Spain, New Zealand, Australia, USA and now being pioneered in South Africa. Other commercially grown truffles include Tuber aestivum (summer truffle), Tuber brumale (winter truffle), Tuber uncinatum (Burgundy truffle) Tuber borchii and Tuber indicum (Chinese truffle). Many people confuse mushrooms and truffles, which are both fungi, but mushrooms do not have the culinary or financial value of truffles. Some mushrooms, such as Porcini (Boletus edulis), are even referred to as truffles because they are also found in forests. Another common confusion is between truffles and terfezia, so-called desert truffles, of which the Kalahari 'truffle' is an example.