A hexadecimal number is a base-16 numeral system that uses sixteen distinct symbols: the digits 0 to 9 and the letters A to F. In this system, A represents ten, B represents eleven, C represents twelve, D represents thirteen, E represents fourteen, and F represents fifteen. Hexadecimal is commonly used in computing and digital electronics because it can represent large binary numbers in a more compact and readable form. Hexadecimal numbers are often used in programming and web design, particularly in defining colors in HTML and CSS. For example, the color white is represented as #FFFFFF, where each pair of characters corresponds to the red, green, and blue components of the color. This system simplifies the representation of binary data, making it easier for developers to work with and understand complex information.