A prune is a dried plum, most commonly from the European plum tree. Not all plum species or varieties can be dried into prunes. A prune is the firm-fleshed fruit (plum) of Prunus domestica varieties that have a high soluble solids content, and do not ferment during drying. Use of the term "prune" for fresh plums is obsolete except when applied to varieties of plum grown for drying.
Prunes
Raw, fresh prune plums that have not been dried into prunes
Prunes in chocolate with an almond in the middle
Moroccan-style tagine of lamb with prunes and almonds
A plum is a fruit of some species in Prunus subg. Prunus. Dried plums are most often called prunes, though in the United States they may be just labeled as 'dried plums', especially during the 21st century.
African Rose plums (Japanese or Chinese plum).
Plum flowers
Plum unripe fruits
Japanese or Chinese plum