When we use SSH terminal to do something on the server side, we can't close the SSH terminal if the task/process is still running on the server side.
TMUX can help it.
1.open SSH terminal
2.login to the server
3.tmux new
4.do your job
5.Ctrl + B then type d to detach the tmux session.
6.logout and Close SSH terminal.
When you have time, you can go back and login to the server, type 'tmux a' then you can attach to your previous tmux session.
TMUX also has function of split windows of terminal.