well I have some queries about "virtual terminals"
The first this is that when a person first logs in if he is using X-session he will be log in to runlevel 5 and the F7 key will be taken by that session . this means that F1 key should also be taken for "First virtual terminal" coz F1 and F7 are linked, am i right? I this is the case, then when i do the ctrl+Alt+F1, it takes me to start the second virtual terminal. but why it alows me to log in at F1 , isn't it already taken by the initial login.
and suppose i have started a second virtual terminal at F2 and then as i type startx to open a corresponding X-session it gives error , this is because F7 is already running the initial X-session, well when i type startx--:1, it starts X-session at F8,okie that is cool. But when i login at F2 and type startx--:2, it should start X-session at F9 but it still starts X-session at F8, why is that.
could some one please tell me how it works and how these Fkeys are likned with virtual terminals and the corresponding X-sessions. could some one pelase recommend me a online tutorial which explains this well. Please reply soon.

No, you're confused. Logins aren't "taken" by a virtual terminal, you can login as many times as you like, virtual terminals are just a convenient way to switch between them.