Cydonia oblonga is a fruit tree with large yellow fruits that resemble a pear or apple. Raw quinces are hard and bitter, but when cooked they acquire a sweet and sour taste. In the past, quinces were used to scent laundry because of their strong aromatic scent.
Chaenomeles japonica, on the other hand, is more of an ornamental plant, with beautiful red flowers in early spring. Its fruits are smaller, green to yellowish, and look like small apples. They are also edible, but very sour and hard, so they are most often used to make marmalades.