The Morse Unit is a unit of measurement used in telegraphy, which is the long-distance transmission of written messages. It is based on a system of dots and dashes, also known as 'dits' and 'dahs'. The Morse Unit is composed of three letters: DOT (3 letters), DAH (3 letters), and DIT (3 letters). The DOT represents a short burst of sound, while the DAH is a longer burst. The DIT is a combination of the two, representing a medium-length burst of sound.