Stain sealants are designed to protect surfaces from discoloration, scratches, and other signs of wear. Some types of stain sealants are designed to create a barrier between a surface and liquids, while others are designed to prevent moisture from penetrating the surface. The most common type of stain sealant is a penetrating sealant, which penetrates the pores of the surface, creating a protective barrier that is resistant to discoloration and other signs of wear.