Coriander (Coriandrum sativum) is a plant in the Apiaceae family. Its fruit (seeds) are typically called "coriander" while its leaves are called cilantro.
 
Coriander is a source of vitamin C, calcium, magnesium, potassium, and iron. Coriander essential oil might have antibacterial effects. Coriander also contains chemicals that might lower blood pressure by causing blood vessels to dilate and work like a "water pill" (diuretic).
People use coriander for anxiety, constipation, diabetes, indigestion, parasite infections, irritable bowel syndrome (IBS), skin irritation, and many other conditions, but there is no good scientific evidence to support these uses.