Tmux is useful in VPSes because it allows scripts and programs to run 24/7, even when you're disconnected from the VPS. You can have multiple sessions running different scripts simutaneously.
Create a new tmux Session:
tmux new -s SessionName
Attach to a Session
tmux a -t SessionName
or to connect to the last connected session...
tmux a
Dettach from a Session:
Hit ctrl + b, then hit d
Kill a tmux Session:
tmux kill-ses -t SessionName
or if you're already in a session...
tmux kill-ses
List tmux sessions:
tmux ls