Face mask sheets are skincare products designed to hydrate, soothe, and treat the skin. They come pre-soaked in various serums and are made from materials like cotton, hydrogel, or bio-cellulose. To use one, you typically unfold the mask and place it on your clean face, aligning it with your eyes, nose, and mouth. After leaving it on for the recommended time, usually around 15-20 minutes, you remove it and gently pat any remaining serum into your skin. They can target specific skin concerns, such as hydration, brightening, or anti-aging.