Hexadecimal color format, also known as hex color, is a way of representing colors using a combination of numbers and letters. The hexadecimal color format is a six-digit code that is used to define the exact color that is displayed on a computer screen. It consists of three pairs of two-digit numbers, with each pair representing the amount of red, green, and blue (RGB) in the color. Hex color is often used in web design, as it is easy to remember and is supported by most web browsers.

Converting the hex color format to RGB is a relatively simple process. The first step is to break down the hex code into its three parts. Each pair of two-digit numbers represents the amount of red, green, and blue in the color. The first pair of digits represents the amount of red, the second pair of digits represents the amount of green, and the third pair of digits represents the amount of blue.

Once the hex code is broken down into its three parts, the next step is to convert each two-digit number into a decimal number. This is done by first taking the first digit of each pair and multiplying it by 16. This will give you the first number of the decimal number. Then, take the second digit of each pair and add it to the first number. This will give you the full decimal number for each color.

Convert Hex Color Format (#FFFFFF) to RGB:

```
function hs_hex_to_rgb($hex)
{
list($r, $g, $b) = sscanf($hex, "#%02x%02x%02x");
return array($r, $g, $b);
}
```

Converting hex color format to RGB can be a useful tool for web designers. By knowing the exact RGB values of a color, web designers can ensure that the colors they use will be accurately displayed on all web browsers. In addition, converting the hex color format to RGB can also be helpful for graphic designers who are creating logos or other designs that need to be displayed in a certain color.