It's funny but it is just one of those things. We don't know much about fruits that are grown and eaten in other countries. It was a surprise to me to see how many different fruits were in the streets, markets and supermarkets in China.
I'd seen these fruits before - but no one could tell me what they were. Eventually I learned that they were mangosteen. In Shanghai there were several people like this with huge heavy baskets of these fruit. We bought some - which caused quite a bit of amusement, I think because we paid far too much money for our small supply.
The fruit are very tasty - similar to lychees. The dark skin is thick and hard and inside there are wonderful white segments of fruit.
I found them difficult to get into the fruit - in part because we did not have a good knife to use. Perhaps at some time later I can try again. Perhaps I can learn a little bit more about how to use this fruit.