There are two types of stalk celery: green and yellow. Green is the most commonly eaten type in the U.S. Yellow resembles green celery but has a milder taste. Celery Nutrition Info
Celeriac is the root variety of celery. It can be prepared and consumed in the same way as other root vegetables such as potatoes and parsnips. Celeriac Nutrition Info
Smallage is a wild variety of celery. The stalks are not generally eaten but the leaves are used in soups and salads.