This appears to be a type of prune plum. The most common European plums (scientific name Prunus domestica L.)  are elongated, blue types, but other colors are available as well. In the USA, European plums are eaten fresh, as fresh slices in salads and desserts, and processed as puree for baby food, baking, dried fruit as in prunes, and fermented as alcoholic beverages, depending on the varieties.

Hope this helps.