Most prunes are made from Freestone Plums, with easily removable pits, whereas most plums grown for fresh consumption are Clingstone Plums, with pits more difficult to remove).  Containing mild laxatives, prunes and prune juice are a common remedy for constipation and the butt of related jokes, many US distributors started calling them "Dried Plums".  Prunes are used in a variety of ethnic cuisines from stews to puddings.