Morse Code is a code that was created in 1832, and which allow to transmit data via short and long impulsions. The paternity of Morse Code is often assigned to Samuel Morse, though this is considered as controversial. He at least gave the Morse Code his name. The advantage of the Morse Code lies in its simplicity and its universality. In fact the impulsions that allows the data to be transmitted could be sound signals, light signals, visual, analogic, or even numeric. You could transmit data with every way that allow you to produce recognizable impulsions.
The Code Morse principle is actually very simple, it assigns to each symbol (letters, numbers, and some special characters) a value constituted by dots for short impulsions, and by dashes for long impulsions. That way you "just" have to know all the Morse alphabet "by-heart" to decode any message that was coded using Morse code. You can note that we usually add a "/" sign between each word when reading a Morse Code phrase. For instance the two words "MORSE CODE" would be coded this way : -- --- .-. ... . / -.-. --- -.. .
The Morse Code is still in use sometimes by the army, always encrypted, as by individuals for some precise utilizations (for instance at sea or in planes). Radio hams still have frequencies in use that were allocated especially for them. Morse Code was officially disused for maritime communications since the 1st February 1999, it was replaced by satellite communications.