Truffle is a type of FUNGUS that grows underground and is highly sought after for its unique flavor. It is also known as a 'diamond of the kitchen' due to its rarity and high price. The two most common types of truffles are the European black truffle and the Italian white truffle. The term 'truffle' can also refer to the edible tuber of the hognut tree, which is native to North America and is also known as an EARTHNUT.