It was a typewriter ribbon, and the type of terminal it was designed to be used with was a typewriter with communications circuitry, called a "teletypewriter".

It was a typewriter ribbon, and the type of terminal it was designed to be used with was a typewriter with communications circuitry, called a "teletypewriter". This is why the controlling terminal of Unix CLI/TUI processes is called a tty or pty (pseudo-tty).