Source : Free On-Line Dictionary of Computing

terminal emulator
     
        A program that allows a computer to act like a (particular
        brand of) terminal, e.g. a {vt-100}.  The computer thus appears
        as a terminal to the {host} computer and accepts the same
        {escape sequence}s for functions such as cursor positioning
        and clearing the screen.
     
        {xterm} is a terminal emulator for the {X Window System}.
     
        (1995-02-16)