What makes a mushrom a truffle?

Question

I know it's not coated in chocolate.

Answer 1

All mushroom are fungus. Not all fungus are mushroom. A truffle is a fungus, but not a mushroom. They grow under ground at the base of trees, and have not successfully been cultivated. (in other words they are wild and can not be farmed, hence the high price)

Answer 2

Truffles are harvested in Europe with the aid of female pigs or truffle dogs, which are able to detect the strong smell of mature truffles underneath the surface of the ground....They can go for anywhere around $250.00 to $450.00 per pound.