Morse code is a telegraph system (a non-secret code) created by Samuel Morse in the nineteenth century. The code is a series of dots (.) and dashes(-) that make up letters that can either be written, toned, or flashed.
When making Morse code, Samuel visited a sprinters shop to find out what letters were used most often and made those letters the smallest. The most used letter was “E”, so “E” is a dot. “E is followed by “S”, and then by “A”.
Today, Morse in mostly used by amateur radio operators and pilots and is rarely used otherwise.