Confectioners' sugar is a term used in the culinary arts to refer to any of a variety of refined sugars that have been finely ground into a powdery form.
Also known as powdered sugar or 10X sugar, confectioners' sugar is easily dissolved in liquid, which makes it ideally suited for making icings and frostings. Additionally, confectioners' sugar can be used decoratively by lightly dusting it over desserts, baked items and even fruit.
The word confectioner means someone who makes candies and other sweets, thus confectioners' sugar is widely used in candymaking and baking.
Because it's made from ordinary sugar, you can make your own confectioners' sugar. All you need is a coffee grinder. Simply place some ordinary granulated sugar in the coffee grinder and pulse until it's a fine powder. Commercial confectioners' sugar contains about 3 percent cornstarch to prevent caking, but if you're grinding your own and using it right away, caking shouldn't be an issue.
Confectioners' sugar is not the same as superfine sugar, or bakers' sugar. These products are finer than granulated sugar, but not as fine as confectioners' sugar.