Cilantro is the fresh leafy part of the coriander plant. Particularly outside the USA, cilantro may go by other names including dhania, coriander leaves, Chinese parsley and Mexican parsley.
Cilantro has a very different taste from coriander seeds (hence the different name). Cilantro tastes soapy to some people. This difference in perception of the flavor of the leaves may have a genetic cause.
Cilantro should never itself be cooked as heat quickly destroys its delicate flavor. Dried cilantro has very little taste.