Bok choy (also known as pak choi, boc choy, and pok choi) is classified as a Chinese cabbage. It does not look like the round European cabbages found in western supermarkets, or to Napa cabbage. While its white stalks may look like celery, it's part of the cabbage family and does not have the same stringiness. The dark green, crinkly leaves of the most common type are like Romaine lettuce.