Screen GNU

Start screen
Type screen in the terminal
Detach from a screen session (session remains open)
Ctrl+a d
Reattach to an open screen session
screen -D -R
Quit screen completely (session closed)
Ctrl+a Ctrl+\

Controlling windows

Create a new window with a shell and switch to it:
Ctrl+a c
List currently open windows for selection:
Ctrl+a "
Close current window:
Ctrl+a k

Controlling Regions

Using regions allows you to display more than one shell on your terminal.

Split the current region into 2 new ones (note: new region will be blank, you need to switch to it then select a window to display in it):
Ctrl+a S
Switch focus to the next region:
Ctrl+a TAB
Remove the current region:
Ctrl+a X

That should be enough to get started