Coriander is the dried seed or fruit of the Coriandrum sativum plant, which belongs to the parsley family. Cilantro is the leaf of this same plant and surprisingly, its flavor is vastly different from that of coriander. Cilantro has a complex but delicate flavor with a hint of pepper, mint and lemon. Coriander has a sweet, aromatic taste with a touch of citrus. Coriander seeds are native to Southern Europe and the Mediterranean region.
As with all seeds, toasting them will bring out more of the aromatic flavor. If your recipe calls for cracked or crushed coriander, buy whole coriander and crack or crush it yourself (either spin it quickly in a blender or hammer slightly in a sealable bag). This will produce the best, freshest taste.