GNU screen

Or, what sort of things you can do with screen and the commands that control them.

• multiuser
• monitoring
• terminal (allpartial, altscreen, bce, c1, charset, defbce, defbreaktype, defc1, defcharset, defflow, defgr, defencoding, defnonblock, defutf8, defwrap, dumptermcap, encoding, flow, gr, nonblock, dinfo, partial, printcmd, reset, term, termcap, terminfo, termcapinfo, utf8, wrap, zmodem)
• appearance (attrcolor, autonuke, bell_msg, caption, clear, defautonuke, defhstatus, echo, fit, height, info, license, nethack, hardstatus, hstatus, lastmsg, msgminwait, msgwait, sorendition, startup_message, time, vbell, vbell_msg, vbellwait, version, wall, width)
• interface (bind, bindkey, digraph, help, mapdefault, mapnotnext, maptimeout, markkeys, escape, meta, process, stuff, xoff, xon)
• text exchange (bufferfile, copy, crlf, deflog, defescape, defscrollback, defslowpaste, ignorecase, log, logfile, defobuflimit, hardcopy, hardcopy_append, hardcopydir, logtstamp, obuflimit, paste, pastefont, readbuf, readreg, register, removebuf, scrollback, slowpaste, writebuf)
• window management (next, at, blanker, blankerprg, lockscreen, deflogin, defmode, defzombie, idle, kill, login, maxwin, number, other, pow_break, redisplay, screen, select, shelltitle, verbose, windowlist, windows, zombie, defzombie)
• region management (focus, only, remove, resize, split)
• misc (backtick, chdir, colon, command, compacthist, console, debug, defshell, exec, detach, displays, eval, history, password, pow_detach, pow_detach_msg, quit, sessionname, setenv, setsid, shell, sleep, source, suspend, unsetenv)