Jam holds its shape, but is less firm than jelly. When jams are made from a mixture of fruits they are usually called conserves, especially when they contain citrus fruits, nuts, raisins or coconut. Preserves are made of small, whole fruits or pieces of fruits in a clear, thick, slightly gelled syrup. Marmalades are soft, transparent fruit jellies that contain small pieces of fruit or citrus peel. Fruit butters are made from fruit pulp cooked with sugar until thickened.
Sugar helps preserve sweet spreads, contributes flavor and aids in gelling.
Granulated white sugar is most often used to make jelly or jam. You can replace part of the sugar with corn syrup or honey, but too much masks the fruit flavor and changes the gel structure. Use tested recipes for replacing sugar with honey and corn syrup. Don't reduce the amount of sugar in traditional recipes, because a gel won't form, and yeasts and molds may grow in the sweet spreads. Overcooking jam and jelly can break down pectin and prevent proper gelling.