Actually coriander is a plant, every part of which is edible. The most commonly used parts for food preparation are the leaves and seeds. I find ground coriander seed to be beautifully fragrant. Coriander is called cilantro by Spanish speaking and other cultures, not to be confused with culantro.
In leaf form, cilantro can have a stronger taste that some find unpalatable. There may be genetic reasons for this; some compounds are known to be tastable
or smellable only by those with given genetic characteristics.