Screen is a full-screen window manager that multiplexes a physical terminal between several processes — man page
Screen allows you to start multiple SSH sessions in a single window. When you disconnect (on purpose or not), your tasks continue running and you can reconnect later as if you never left! There are much more in-depth posts about screen, like here and here. This one is just a reference of common commands—public notes—that I can refer back to as needed.
screen -S dave — Create a named session
ctrl-a, d — Exit screen
screen -list — List screen sessions
screen -r dave — Resume a named session
ctrl-a, S – Split the window horizontally into 2 panes
ctrl-a, <tab> — Toggle between panes
ctrl-a, X — Close pane (X not x)
ctrl-a, x — Password-lock the screen
ctrl-a, w — List windows
ctrl-a, 0 — Switch to window 0 in current pane
ctrl-a, c — Create a new shell
ctrl-a, :resize 70% — Make pane larger
ctrl-a :layout save default — Remember window splits and sizes