A terminal emulator, terminal application, term, or tty for short, is a program that emulates a "dumb" video terminal within some other display architecture. Though typically synonymous with a command line shell or text terminal, the term terminal covers all remote terminals, including graphical interfaces. A terminal emulator inside a graphical user interface is often called a terminal window.
Fonts for most X terminals can be configured in ~/.Xdefaults. An example of this is: