Twin is a windowing environment with mouse support, window manager, terminal emulator and networked clients, all inside a text display. It supports a variety of displays:

- plain text terminals (any termcap/ncurses compatible terminal, Linux console, twin's own terminal emulator); - X11, where it can be used as a multi-window xterm; - itself (you can display a twin on another twin); - twdisplay, a general network-transparent display client, used to attach/detach more displays on-the-fly.