A cupcake (or fairy cake) is a small cake designed to serve one person, usually made in a small paper cup container. As with larger cakes, frosting and other decorations are usually applied.
Cupcakes are often served during a celebration, such as children's classroom birthday parties. They are a more convenient alternative to cake because they don't require plates, utensils, or dividing into pieces.
A simple cupcake uses the same ingredients as most other standard cakes - incorporating butter, white refined sugar, eggs, and flour.
The name "cup" cakes or "measure" cakes is believed to have developed because of the use of the practice of measuring the ingredients using a standard-sized cup instead of the previous practice of weighing the ingredients. The fact that these little cakes were baked in cup-shaped muffin baking containers gave double-meaning to the term "cup cake", and was probably the main factor for "cupcake" becoming the U.S. standard term.
It is also possible that cupcakes came into being simply as smaller versions of the Victoria sponge cake, as the mixture required is exactly the same. The mixture is also the same as the quarter cake recipe, so called because it is made up of four ingredients in equal ratios; butter, self-raising flour, eggs and caster sugar.
It's interesting to note that the cakes were likely called "number" cakes because of a mnemonic device for remembering the recipe: One cup of butter, two cups of sugar, three cups of flour and four eggs plus one cup of milk and one spoonful of soda.