tmux – terminal multiplexer
tmux is a terminal multiplexer: it enables a number of terminals to be created, accessed, and controlled from a single screen. tmux may be detached from a screen and continue running in the background, then later reattached.
When tmux is started it creates a new session with a single window and displays it on screen. A status line at the bottom of the screen shows information on the current session and is used to enter interactive commands.