Missing pieces

Imagine tiling window manager(with only horizontal tiles) and session management like VNC, but for terminal. You'll get program that can manage number of terminal sessions and keeps them running even after you log out. That makes it popular among people who have remote shell account and run IRC client there. Though most people know only about fraction of the useful features it has. It's available for most Unix-like operating systems out there. Some Linux distributions might have installed by default.

You can start it by typing:

screen

By default this displays license and then open shell, but you can define it to start up predefined list of programs. At that point it's hard to tell if Screen is running or not. One way to check it is to try to change window. You can do that by pressing control+a and then 0 (which is number of the first window). If Screen is running, it notifies that window 0 is already open.

You can detach the session by pressing control+a and then ctrl+d. To resume the session, you can type:

screen -r

Though if for some reason Screen is already attached you have to use:

screen -dr

If you want to attach session, without detaching already running session, you can also use:

screen -x

Though keep in mind, screen size is always same in all the attached sessions, so if you want to use whole screen (or shrink to see everything type: control+a and F.

To quit and close all windows, type control+a :quit.

I'll end with summary of commands I use most often (you can always read the manual, if you want to see the full list). Line that starts with screen is command line option. Other commands are typed when screen is runnig.

Attaching and detaching session

Start new session: screen
Attach a session: screen -r
Detach and then attach a session: screen -dr
Share session: screen -x

Working with windows
Create new window: control+a c
Change to window number 1:control+a 1
Change to previously open window: control+a control+a
Go to next window: control+a n
Go to previous window: control+a p

Window tiling
Split window:control+a S
Focus next region:control+a tab
Remove region:control+a X
Remove all regions: control+a Q

Monitoring windows
Monitor for activity: control+a M
Monitor for inactivity: control+a _

Working with multiple sessions
List sessions: screen -ls
Resume session: screen -r session_name
Rename session: control+a :sessionname name
Quitting
quit and close all windows permanently: control+a :quit