if you’re a nail polish novice, you’re probably confused about base coat and top coat. What are these? A base coat is a layer that is applied to your nails before your chosen nail polish shade. Their function is to prepare the nail for the polish that you will apply over it, and also to prevent nails from being stained by the colouredpolish. A top coat, on the other hand, is what you apply over your nail polish to prevent the polish from chipping or fading