Marmalade is a British preserve commonly made from oranges. Orange marmalade sometimes includes small pieces of orange peel along with the jam.
Marmalade is often made with Seville oranges, so named because it originated in Seville, Spain. Seville oranges are favoured because they have a higher concentration of pectin than most other types of oranges. The higher pectin content tends to make the marmalade set better than it would otherwise.