Cakes - Broadly defined, cakes are any flat, round disk of food. The earliest cakes are believed to come from ancient Egypt but they were really sweet breads. Cake recipes that are similar to today and contain beaten eggs date from the 17th Century. Most of us think of cakes as a sweet, baked confection made with or without fat (butter, oil, or shortening) and usually containing a mixture or batter of flour, sugar, eggs, flavorings and sometimes another leavener such as baking powder or baking soda.

Cupcake - The name given to a small individual cake that is baked in a cup-shaped mold (usually a muffin pan).

Frosting - What is the proper name for that sweet sugary mixture used to fill and cover cakes, pastries and other confections? The answer may depend on where you live. Americans tend to use the word 'frosting'. Other countries tend to use the word 'icing'. The name 'icing' probably has something to do with the fact that 'confectioners' or 'powdered' sugar is also known as 'icing' sugar. Hence, combining icing sugar with other ingredients makes an 'icing'. The fact is that 'frosting' and 'icing' are the same thing and food writers used them interchangeably.

Ganache - A French term referring to a smooth mixture of chopped chocolate and heavy cream.

Glaze - Defined as a thin liquid sweet coating that adds shine and color to pastries. Also used as a protective coating to prevent the fruit on the top of tarts from drying out and looking unattractive.

Buttercream - Is a name that encompasses a broad range of icings that can differ by person, city, region, or country. They can be quick or complicated to make depending on whether they are cooked or uncooked. Buttercreams may contain powdered sugar, white granulated sugar, whole eggs, egg whites, egg yolks, unsalted butter, shortening, milk or cream, pastry cream, fondant, and various flavorings (extract, purée, chocolate, liqueur). Generally, buttercream is a light and creamy smooth icing used to fill, frost and decorate (flowers, leaves, etc.) all kinds of cakes and pastries. There are several types of buttercream :

American buttercream (normal buttercream) = shortening, powdered sugar.   Sometimes egg whites are added for smoothness and consistency. ( I like these on cupcakes- the sweetest of all buttercreams)

Italian buttercream  =  hot sugar syrup brought to med. ball stage, whipped into egg whites at the soft-peak stage, whipped until cold, then butter added.

genoise buttercream  = whole eggs warmed with sugar, whipped, add butter.
french buttercream  = same method as Italian only use all egg yolks instead of whites.  Egg yolks are brought to the au ribbon stage before the sugar syrup is beaten in.
Anglais buttercream = creme anglais with enough butter whipped into make it spreadable.
Swiss buttercream  =  sugar and whites warmed together, whipped to med-firm peaks, butter added.

(My favourite so far and the special buttercream that I offer for wedding cakes)
Taken from the Whisk Kid - "Swiss Meringue buttercream was the first European-style buttercream I ever made. It's a little easier than Italian Meringue buttercream and it uses nearly the same exact proportions of ingredients. The taste is identical, but the difference is evident in the texture; Swiss Meringue Buttercream is a little less light than its Italian cousin, and feels a little heavier (but not oily!) on the tongue."
Decoration wise however, buttercream has its limitations despite its deliciousness.

Fondant - a soft pliable preparation of sugar, water, and flavorings that is used as a basis for candies or icings. (Personally, I don't really eat fondant but it is the BEST icing to use for sculpted decoration to give a clean look on a cake and basically the most versatile form of icing for a decorator. I usually put buttercream below the fondant to have the best of both worlds.)

Filling - a food mixture used to fill pastry, cakes or sandwiches