It's sour horn. Peel off the skin, remove the tendons inside and eat brown pulp. There are hard stones in the pulp, and stones can't be eaten. Sour horns are divided into sour horns and sweet horns. Sour horns are sour and are not recommended to be eaten directly. You can eat it with sugar, or you can make sour horn juice. Sweet horns can be eaten directly, which is a bit sour.