What's the difference between jam and marmalade ?
Marmalade is made from citrus fruits. Originally, marmalade was made from quinces -- the word comes from 'marmelo', which is Portuguese for quince.
Marmalade is made by boiling the juice, pulp and peel of the fruit with sugar and water.
Jam can be made from any fruit (or even vegetables in some cases) and just refers to a preserve made by boiling the fruit (or veg!) with sugar.
Marrow and rhubarb are two vegetables that are commonly made into jam.