Coriander is an annual herb in the family Apiaceae. It is also known as Chinese parsley, dhania or cilantro. All parts of the plant are edible, but the fresh leaves and the dried seeds (as a spice) are the parts most traditionally used in cooking.
Most people perceive the taste of coriander leaves as a tart, lemon/lime taste. The dried cilantro spice is good for people just acquiring a taste for cilantro, as their flavor is milder than the fresh herb.