If you would rather, the Main Menu can stay collapsed or expanded. You can change this setting in the User Preferences menu. This setting is local, so will only apply to the browser you are currently using. If you do not allow cookies this will not work.

If you set the menu to stay closed you can still see what each icon in the menu does by hovering over the icon. The stay closed option is advised for small screens, and the stay open option is useful while you are getting used to the system, but for a best of both worlds the dynamic open/close gives the main content plenty of room on your screen while you can still see what everything does when you hover over the menu.