A roller blind is a type of window covering that consists of a single piece of fabric or material that rolls up and down on a cylindrical tube. The fabric is typically controlled by a chain, cord, or motorized mechanism, allowing the user to adjust the amount of light and privacy in a room. Roller blinds come in a wide range of materials, including light-filtering fabrics, blackout fabrics, and sunscreen fabrics, offering different levels of light control and privacy. They are popular for their sleek, minimalist design and practicality.