New password after restoring iPod Touch from backup
The passcode would be whatever the passcode was at the time of the backup you restored to. When you restore an iOS device from a backup, it puts all the software configuration back on the device, including the passcode that was set at the time. 

If you want to get past this passcode, I suggest trying all your most recent passcodes. Be careful though, after a certain number of attempts your iPod may lock you out and prevent you from entering any more passcodes.

You can remove the passcode, but you will have to restore your iPod and you will not be able to restore from a backup.

You can do this by:


Plug your iPhone into a computer running the latest version of iTunes.
Hold the home button and the sleep/wake button for exactly 8 seconds.
After this 8 seconds is up, release the sleep/wake button, but continue to hold the home button until iTunes recognizes your iPhone.
Then, choose the Restore option (this should be the only option) and wait for iTunes to download the necessary software and restore your iPhone.