What does tmux add to your terminal?
A tmux session can contain windows, and a window can contain several panes. A pane is one visible area running a shell or another terminal program. For example, one pane can show the output of a local test while another is available for your next command.
What happens when you leave a session?
Detaching closes your view of the session. The programs can keep running as long as the tmux server on that computer and their session stay alive. Reattach on the same computer to return to it. A reboot or terminated server ends those running sessions. Save your work separately.
What can you keep when moving to another computer?
tmux is open source and runs inside a terminal on supported Unix-like systems. It must be available on the computer where the session runs. Keep the configuration you need, usually a file such as .tmux.conf, and copy your project files separately. Review any commands in the configuration before loading it. A configuration file can rebuild your preferences, while the running session belongs to the original computer.
How would you tell two panes apart before typing?
Draw a local session called sample-shop with one pane for a fictional test result and one for commands. Mark which pane is active and write the folder you expect its shell to report. Draw the session continuing after you detach, then cross it out for the case where the computer restarts. Use paper if the machine or session is unclear.