Celeriac is kin to the stalk celery you see in the stores. Flavor is the same. However, with root celery, you eat the large round root section not the stalk. Peel the outer skin to eat. It is good raw added to salads or slaws. You can also boil and/or mash it for soups (like potato or leek soup) or stews. The flavor is great and the texture is smooth (no fiber strings like regular stalk celery).