The clean screen mode

In clean screen mode, you can maximize the drawing area by dismissing user interface elements, such as the menu bar, the ribbon, toolbars, panels, the Command line, status bar and document tabs.

You can still use the Quad to launch commands.

Press and hold the Ctrl key and press the 0 (zero) key to toggle the clean screen mode on/off.
Note: Do not use the numeric keypad.
Note: On AZERTY keyboards: do not press the Shift key when hitting the 0 key.