A font provides a resource containing the visual representation of characters. At the simplest level it contains information that maps character codes to shapes (called glyphs) that represent these characters. Fonts sharing a common design style are commonly grouped into font families classified by a set of standard font properties. Within a family, the shape displayed for a given character can vary by stroke weight, slant or relative width, among others. A given font face is described by a unique combination of these properties. For a given range of text, CSS font properties are used to select a font family and a specific font face within that family to be used when rendering that text.