Marmalade is often referred to as preserves made with citrus, that include the rind or peel, along with the pulp and fruit.  The fruit is boiled with sugar and pectin and often contains large chunks of fruit and rind. Jam includes whole, cut fruit that is cooked down with sugar and pectin.  Like marmalade, it also has large pieces of fruit to give it more structure. Since tomato jam contains peel and large pieces of fruit that are boiled down with sugar, it can be referred to as either a jam or a marmalade.