For today's recipe, we used dark brown sugar in the caramel cake and frosting. However, we have also used light brown sugar for this recipe. Both are delicious. Brown sugar is white sugar with the addition of molasses. Dark brown sugar has more molasses (about double the amount) as light brown sugar and therefore has a deeper color and flavor. Light brown sugar, which we've used in many of our recipes including our Banana Pound Cake, Chocolate Chip Cake, and Pineapple Upside Down Bundt Cake has a milder flavor.