Features
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.
You get then the following functionalities
Protect running programs on a remote server from connection drops by running them inside tmux.
Allow programs running on a remote server to be accessed from multiple different local computers.
Work with multiple programs and shells together in one terminal, a bit like a window manager (You can switch by name)
ie you can close the Xterm and come back.