Binary system might be what computers use, but the hexadecimal number system is the closest one to it that us humans can comprehend. One of the unique properties of a hexadecimal number is that it can be easily converted to binary digits. All you need is the conversion chart shown below that maps all hex digits with their binary equivalents.
Hex is used in HTML to represent colors. For example, FF0000 refers to the color red. It is also used by Hex editors to display binary data stored in files. Any byte from 0-255 can be represented using two hexadecimal digits. 00 represents the NULL character whose byte value is 0 and FF represents 'ÿ' (the latin small letter y with diaeresis). Thus, a hex digit represents a nibble and two of them represent a byte.