The taste of a black truffle can actually vary depending where it was harvested from. A general description of a black truffle's flavor is nutty and somewhat woody with a slight mushroom taste. A cheap way to find out how truffles taste is to buy truffle oil.
Truffles are the most expensive food in the world according to CBS and considered a rare delicacy, but truffle oil is much cheaper and gives foodies a taste before they spend a lot of money. Buying real truffles later is possible if the truffle oil is a taste that is agreeable when used in cooking.