Vanilla is a flavoring derived from the vanilla bean. Vanillin is the distinctive chemical in vanilla. Vanilla is commonly used in desserts and in chocolate. Vanilla is often not noticeable as a distinct flavor, yet nevertheless greatly improves the taste of the dish it has been added to (much like salt and MSG).
Vanilla extract is alcohol containing flavor (vanillin) from the vanilla bean. Vanillin itself, produced by a modern chemical process, is widely sold in a form similar to vanilla extract. When a recipe specifies vanilla, usually the recipe is intended to work with either vanilla extract or vanillin. Such recipes will require modification if whole vanilla beans are used.
Vanilla is also used in the form of vanilla sugar. This can have different meanings depending upon the origin of the recipe. In Scandinavian countries, vanilla sugar is a powdered sugar with a strong vanilla flavour. In these countries, it is the main method of incorporating vanilla flavor into a recipe; vanilla extract is not commonly available. This form of vanilla sugar can be replaced by a roughly equivalent volume of vanilla extract. In other countries, including the United States, vanilla sugar usually is granulated white sugar that has been flavored over some time by a vanilla bean included in the sugar.