And what does the L represent? Well, to demonstrate the meaning behind the D and the L letters, let's take a look at another type of carbohydrate molecule, namely erythros. So let's compare D erythros and L erythros. Notice what the D and the L mean is these will be mirror images with respect to one another. These are known as enantomers. So sugars that are mirror images of one another are known as enantomers.