Suppose you are working on your office server and want to save the session and resume it from another location like suppose from your home. screen command is used for this purpose. Let us take an easy example to understand it. Suppose you are on console 2 (alt+ctrl+f2) and issue following commands
root# screen -S test
Now move to console 3 (alt+ctrl+f3) and type following command
root# screen -d -R test (here -R is to restore the session)
Check the output , i hope you got the magic of screen command. To exit from session use exit command.