A mango fork is a three-tined fork with one long, center tine and two shorter side tines. The fork is designed to hold a mango like a lollipop so it can be easily peeled and eaten (in theory at least).
To use the fork, insert the long center tine into the bottom, wide end of the mango pit. Now the mango can be peeled like a banana. See more information about the fork and where to buy, below.
You can read more about the history of the mango fork here.