Icing sugar, also known as powdered sugar or confectioners' sugar, is a finely ground form of sugar that is commonly used in baking and dessert making. It is made by grinding granulated sugar into a very fine powder, and then mixing it with a small amount of cornstarch to prevent caking.

Icing sugar is most commonly used as a decorative topping for cakes, cookies, and pastries, as well as in frosting, glazes, and fillings. Its fine texture allows it to dissolve quickly and evenly, providing a smooth, creamy texture to many desserts. It can also be used as a dusting for chocolates, truffles, or other sweet treats.

Icing sugar comes in different grades of fineness, with the most common being extra-fine and superfine. The grade of icing sugar used can impact the texture of the finished product, with finer grades providing a smoother, more delicate finish.

In addition to its culinary uses, icing sugar is also used in other applications, such as in the production of pharmaceuticals, cosmetics, and even printer ink.

Overall, icing sugar is a versatile and essential ingredient in many dessert recipes, providing sweetness, texture, and visual appeal to baked goods and other treats.