Fennel is a vegetable with 3 main edible parts: bulb, foliage, and seed. The bulb is white and to me it is the best part of the plant when cooked (see recipe below). The green foliage of the fennel resembles celery and dill. Typically the fennel you find in the stores will not have the seeds attached, as they are sold separately for a high price.
Fennel is indigenous to the shores of the Mediterranean, according to Wikipedia.
The bulb of the fennel is best when cooked by roasting, braising, or sautéing it. The leafy green part of the fennel is often used to make stock or sliced thinly and added to salads.