Granulated sugar
This
white,
granular, crystalline sugar is what to use when a recipe calls for sugar without specifying a particular type. White sugar is most commonly available in a fine granulation, though superfine (also called ultrafine or castor sugar), a finer grind, is also available. Because superfine sugar dissolves readily, it's ideal for frostings, meringues, and drinks.
Also see
Brown Sugar, Raw Sugar, Powdered Sugar, Jaggery, Molasses