Some people refer to celeriac as celery root, but it is not the root of a celery stalk.  It belongs to the same plant family as carrots and is related to celery, parsley, and parsnips.

The edible part of the celeriac plant is the root.  Celeriac has a fantastic crunch and a super nutty, celery-like flavour that makes it perfect for salads and slaws. Cooked, it takes on a slight sweetness that works well mashed, baked, roasted or boiled.