A problem (probably conceptual) with snapshot

Today I needed to install Oracle and some other things on my PC, but I realize that it would be better to make a snapshot and then reboot Linux with this snapshot mounted instead of root.
Ok, I did that and changed fstab to mount my snapRoot instead root, ok...I saw with 'df' command that it worked.
And I've installed all what I wanted, some garbage too...by the way, this snapRoot doesnt means nothing to me, just for testing. And then I changed the fstab again to mount the root original. But after it, all the changes I made on snapshot was made on my root LV too. And the lvdisplay command shows something strange now, about these two LV's. The output is:

--- Logical volume ---

 LV Name                /dev/dutcheVG/root
 VG Name                dutcheVG
 LV UUID                aAN6BH-GqW3-zhtr-KeIt-BW4m-qEyw-RypMit
 LV Write Access        read/write
 LV snapshot status     source of
                        /dev/dutcheVG/snap_root [INACTIVE]
 LV Status              available
 # open                 0
 LV Size                9.27 GB
 Current LE             2372
 Segments               1
 Allocation             inherit
 Read ahead sectors     0
 Block device           254:5

--- Logical volume ---

 LV Name                /dev/dutcheVG/snap_root
 VG Name                dutcheVG
 LV UUID                cj2PD2-4OYX-eCzw-kG5y-r071-icK0-dq7FBr
 LV Write Access        read/write
 LV snapshot status     INACTIVE destination for /dev/dutcheVG/root
 LV Status              NOT available
 LV Size                9.27 GB
 Current LE             2372
 COW-table size         2.00 GB
 COW-table LE           512
 Snapshot chunk size    8.00 KB
 Segments               1
 Allocation             inherit
 Read ahead sectors     0

I donno what is really happening, does anybody can explain me? Plz!!

Thanks in advance