Screen is a full-screen window manager that multiplexes a physical terminal between several processes
You can enter copy mode with Ctrl-A [
If you are using copy mode for scrollback only, it can be exited at any time with the Esc key.
To copy text, maneuver the cursor to the beginning of the desired text, and press the spacebar to mark it. Then position the cursor over the end of the text you'd like and press the spacebar again to mark it. When you mark the end, the text is copied into screen's internal copy buffer, and copy mode is exited. You can paste the text in your copy buffer into the active window with Ctrl-A ].
C-a C-i (info) Show info about this window.
C-a C-k (kill) Destroy current window.
C-a C-l (redisplay) Fully refresh current window.
C-a C-\ (quit) Kill all windows and terminate screen.
C-a esc (copy) Enter copy/scrollback mode.
C-a ] (paste .) Write the contents of the paste buffer to the stdin queue of the current window.