icing and frosting

Icing, also called frosting, is a sweet glaze made of sugar that often also contains butter, water, egg whites, milk, or flavorings and is used to cover or decorate baked goods, such as cakes or cookies.

Icing can be formed into shapes such as flowers and leaves using a pastry bag. Such decorations commonly grace birthday and wedding cakes. Chef's color dye (food coloring) is commonly added to icing mixtures to achieve the desired color. Sprinkles, coloring mist, edible images or other decorations are often used on top of icing.

They are both used on making cakes.

To make it please follow the following steps:

The simplest icing is a glac icing, containing icing sugar and water. This can be flavored and colored as desired, for example by using lemon juice in place of the water. More complicated icings can be made by beating fat into icing sugar (as in butter cream), by melting fat and sugar together, by using egg whites (as in royal icing), and by adding other ingredients such as glycerin (as in fondant). Some icings can be made from combinations of sugar and cream cheeses, or by using ground almonds (as in marzipan).

Icing can be applied with a utensil such as a knife or spatula, or it can be applied by drizzling or dipping (see glaze) or by rolling the icing out and draping it over the cake. The method of application largely depends on the type and texture of icing being used. Icing may be used between layers in a cake as a filling, or it may be used to completely or partially cover the outside of a cake or other baked product.

http://en.wikipedia.org/wiki/Icing_%28food%29