Carpet runners/stair runners are a piece of carpet that doesn't cover the entire width of the stairs. They come in various colors and patterns and in various widths. One reason you may want to add a runner may be for safety purposes. Wood or tiled floors can be slippery which may pose a danger for children, pets, or those with mobility issues. In addition, carpet absorbs noise much more than hard surfaces so making your trip up and down the stairs will be much quieter. Finally, adding a carpet runner adds style to your home.