As nouns the difference between marmalade and biscotin

is that marmalade is citrus fruit variant of jam but distinguished by being made slightly bitter by the addition of the peel and by partial caramelisation during manufacture most commonly made with seville oranges, and usually qualified by the name of the fruit when made with other types of fruit while biscotin is a confection made of flour, sugar, marmalade, and eggs; a sweet biscuit.

As a verb marmalade

is to spread marmalade on.