What is a mangosteen???

The mangosteen grows on small evergreen trees in Malaysia, Thailand, Indonesia and southern India. Some farmers are trying their luck in Hawaii and the Caribbean, but the fruit is known for being difficult to grow. It is said that Queen Victoria offered a sizable prize to anyone who could bring an edible mangosteen back to England, but no one was able. Mangosteens are currently not available in the United States because the rind can carry pests that would threaten other crops.
The mangosteen is a round, purple fruit slightly smaller than a tennis ball. To eat it, you can crush the brittle yet moist rind with your palms to reveal the pure-white delicacy inside. The bitter rind is inedible, and the fruit comes in the form of variously sized wedged segments, the largest of which may hold a solitary seed. The number of segments usually varies from 4 to 8 which is matched by the number of points on the protrusion from the underside of the fruit; therefore, you can discover how many segments you are in for before you open the mangosteen.
The flavor? Its really not like anything else you may have tasted, so do not take comparisons too literally. The mangosteen has flavors that range from strawberry, peach, vanilla ice cream - it is definitely sweet tempered with a very slight sourness. The flavor is divine and wonderfully delicate. You can find canned mangosteen, but the flavor does not even seem to resemble that of the fresh fruit. There is a new electronic pasteurization process that may allow mangosteens to be shipped to the U.S. mainland from Hawaii, but they won't be readily available anytime soon.

Article taken from: http://www.wisegeek.com/what-is-a-mangosteen.htm