A sheet mask is a skincare product made from a thin sheet of fabric or paper that is soaked in a serum or essence. It is designed to fit over the face, providing concentrated hydration and nutrients to the skin. Users typically apply the mask for a set period, usually 15 to 30 minutes, allowing the ingredients to penetrate the skin effectively. These masks come in various formulations, targeting different skin concerns such as dryness, acne, or aging. They are popular for their convenience and ease of use, making them a favorite in many people's skincare routines.