A makeup primer is a cosmetic product applied before foundation and other makeup to create a smooth and even base for better makeup application. It typically comes in a gel, cream, or liquid form and is designed to fill in fine lines, pores, and imperfections, creating a flawless canvas for makeup. Primers often contain ingredients that help makeup adhere better to the skin, prolong its wear, and provide a smoother finish. Additionally, some primers may have added benefits such as hydrating the skin, controlling oil, or reducing redness. Overall, makeup primers help enhance the longevity and performance of makeup while improving the overall look of the skin.