The quince, or Cydonia oblonga, is the sole member of the genus Cydonia and native to warm-temperate southwest Asia in the Caucasus region. It is a small, deciduous tree, growing 5–8 m tall and 4–6 m wide, related toapples and pears, and like them has a pome fruit, which is bright golden yellow when mature, pear-shaped, 7–12 cm long and 6–9 cm broad.
Most varieties of quince are too hard, astringent and sour to eat raw unless ‘bletted’ (softened by frost and subsequent decay). High in pectin, they are used to make jam, jelly and quince pudding, or they may be peeled, then roasted, baked or stewed. The flesh of the fruit turns red after a long cooking time. The very strong perfume means they can be added in small quantities to apple pies and jam to enhance the flavour. Adding a diced quince to apple sauce will enhance the taste of the apple sauce with the chunks of relatively firm, tart quince. The term “marmalade”, originally meaning a quince jam, derives from “marmelo,” the Portuguese word for this fruit. [ Source: Wikipedia ]
Other uses include wine, a tea additive and some medicinal uses.