Icing is a smooth, sweet topping used to cover or accent cakes, cupcakes, cookies, and other baked goods. It can range from thin glazes that lightly coat a surface to thicker spreads that create defined layers and help decorate edges and details. Because icing sits on the exterior of a bake, it plays a key role in both texture and appearance, providing a finishing surface that can be shaped, smoothed, or patterned before it sets. Different types of icing behave in characteristic ways. A simple powdered sugar and liquid glaze sets to a thin sheen, making it suitable for drizzling over buns, muffins, and loaf cakes.

Buttercream and richer icing formulas have more body, allowing them to be spread with a spatula, smoothed for a flat finish, or built up for piped detail. When icing is applied while a cake is still slightly warm, it can meld into the surface and create a smooth bond; when applied to a cooled bake, it holds sharper lines and textures. Icing also interacts with other decorative elements. Sprinkles, dusting powders, and shaped chocolates adhere to its surface as it sets, letting you combine color, texture, and form in a single piece. Because it can be tinted with food color or layered with fillings, icing supports both simple finishes and more involved decorating without changing the structure of the baked item beneath.