While there are numerous lip shapes, they’re generally split into two categories: full or thin. If your lips are full, they’re likely to appear voluminous and pillowy. Thin lips, meanwhile, tend to be less prominent. As for why it matters: Knowing your basic lip shape can help you determine the best way to apply your lip makeup. For example, if you have thin lips and want to make them look plumper, over-lining with a lip liner and topping with a reflective lip gloss can help create a fuller lip look. Lip liner can also be used to define and balance specific features, like your cupid’s bow.