Light corn syrup is mixed with salt and vanilla, and is sometimes referred to as white corn syrup. The term light refers to the color of the syrup, not the calorie content. Light corn syrup has a delicately sweet flavor.
Dark corn syrup is mixed with a type of refiner's syrup or molasses, caramel and salt and has a decidedly bolder flavor than light corn syrup.
Light and dark corn syrups have similar functions. The dark variety tends to add more flavor, so is more commonly used in baked goods and barbecue sauces. Light corn syrup, with its light sweet flavor, is used in fruit jams and jellies. The syrups can be used interchangeably depending upon the recipe or personal preference.