A shower curtain liner is a waterproof or water-resistant sheet that hangs inside a shower or bathtub. Its primary purpose is to prevent water from splashing outside the shower area, protecting the bathroom floor from moisture and potential water damage. Liners are typically made from materials like vinyl, PEVA, or polyester, which are easy to clean and maintain. These liners come in various sizes and styles to fit different shower setups. Many are designed to be used in conjunction with a decorative shower curtain, providing both functionality and aesthetic appeal. Regular cleaning and replacement of liners can help maintain a fresh and hygienic bathroom environment.