Pressing OK will give you the kdm or gdm ( the login manager your distro uses ) to log in and after logging in you will have the 2 sessions running . . . . hint: you can even have a KDE and a Gnome session running at the same time.
As soon as you log out in one session you will automatically be switched over to the other session . . . isn't that cool ??
Note: Next to the F8 you can start additional X-sessions on the F9, F10, F11 and F12 keys too, so you can have a maximum of 6 text- plus 6 X-sessions which is total of 12 sessions running at the same time on only one computer.
-- May 31 2005 ( Revised Dec 15 2005 ) --