As far as your main Windows installation is concerned, a VM is just another application -- like Notepad. You can minimize the window, run it full screen, move it around your screen, etc.
Another cool thing about VMs is that you can pause them. Done messing around with Windows 8? Don't shut it down. Just pause/suspend it. Next time you want to run it, resume it. It'll start up much faster than a normal boot.
One other killer feature -- snapshots. Let's say you wanted to really start messing around with Windows 8 and you just downloaded 1337haX0R tool and want to install it. Make a snapshot first. That saves the state of your VM. Then, when the 1337haX0R tool inevitable hoses your Windows 8 VM. You can just revert back to that snapshot as if nothing happened. This is much more reliable than setting a Windows Restore Point and hoping that will actually work.
