Corn syrup is a sweetening ingredient often used in baking and cooking instead of or in addition to sugar or honey. Since it is a liquid sweetener, it mixes easily into drinks and sauces. Most brands of corn syrup, including Karo, offer both light and dark varieties.
Light Corn Syrup
Light corn syrup is a mixture of corn syrup and high-fructose corn syrup, which is a modified, sweeter version. Light corn syrup is flavored with salt and pure vanilla. It is generally clear and colorless and has a moderately sweet flavor. Light refers to the color of the corn syrup, not a reduction in calories or sugar. A "lite" version has fewer calories. Light corn syrup is sometimes referred to as white corn syrup.
Dark Corn Syrup
Dark corn syrup is a mixture of corn syrup and a small amount of refiners' syrup, which is a type of molasses. Dark corn syrup is flavored with caramel and salt. It has a rich brown color and a distinctive, molasses-like flavor.
Dark and light corn syrup can generally be used interchangeably in recipes, though many will specify one or the other. The delicate flavor of light corn syrup is often used in jams or fruit sauces, while dark corn syrup can be used in baked goods.