Classic butter cream: A rich, spreadable frosting made with sugar, water, cream of tartar, eggs and butter.
Fondant: Made with water, sugar, corn syrup or cream of tartar, this classic European cooked icing has a smooth, satiny finish.
Ganache: A combination of chocolate and cream.
Marzipan: Made with almonds, sugar and corn syrup, this is a sweet, supple confection that is easily molded and shaped.
Sponge cake: Contains a higher proportion of eggs in relation to other ingredients and relies on a foam made of eggs or egg whites for leavening. American sponge cakes are more moist and tender than European sponges. Génoise is a sponge enriched with butter. European sponge cakes are usually soaked with syrups, then assembled into opulent layer cakes.
Butter cake: A velvety textured classic American cake that gets its flavor from a high proportion of butter to eggs.
Fillings: Usually less sweet than frostings, these are custardlike or puddinglike mixtures that may contain fruit or other flavorings.
Fruit curd: Often made with lemon, orange or raspberry, these are more tart and less thick than custard or creme fillings.
Source: Joy of Cooking