with tmux you can run persistant sessions on a remote terminal; if you have a big screen it can be very handy to split your terminal into panes. for example read man pages on the left, and try out the information on the commandline in the right pane.
First thing I install.
Cant imagine my work without it any more!
I have a tmux session on a server from my job... since 8 months ago and it still runs smoothly
Screen wasn't such a good name from the beginning.
Tmux is much better, than screen.