It is originally native to the Mediterranean you will also find it in Thai and Chinese cuisine as well as Hispanic and Indian dishes. Interestingly enough this herb is so well known that they are even mentioned in the Bible. Ancient Romans used the herb to preserve meat and it can also be steeped as a tea. Cilantro is said to have stomach soothing properties that when consumed in large quantities, offers a significant source of Vitamins A and C.
Okay, so back to the dual purpose idea, when the plant is new and relatively low to the ground (6-8 inches in height) it is the delicious cilantro. However, what happens is that it will "bolt" in the heat of the summer. This means that it goes to flower as the plant prepares to change to its seed form, a self propagating wonder. Once the stalks rise well above 12-18 inches the plant leaves change to a more carrot top looking spindly type and they begin to flower.
NOTE: Wherever you plant this herb it is likely to perform like a perennial, meaning because it self seeds it will come back year after year. Even the most diligent gardener is usually unable to harvest EVERY seed that drops to the ground so you again have the dual purpose advantage of a re-seeding plant as well as a second herb to use, Coriander.