What is "caster sugar"?

Caster sugar, also known as baker's sugar, is a finely ground sugar with a texture that falls between granulated sugar and powdered sugar. It dissolves quickly, making it ideal for recipes where a smooth texture is desired, such as cakes, cookies, and meringues. Caster sugar is commonly used in baking because it blends easily with other ingredients and helps create a light and airy texture in baked goods.