When configuring the syncing of podcasts between iTunes and a device, it's possible to automatically sync "all unplayed" and "all new" podcasts.
It's not clear to me what the difference is between unplayed and new podcasts. An Apple Support Communities post explains it as follows:
Unplayed podcasts, are those that have previously been synced to your iPod, but have yet to be played while new podcasts are those that have been synced to your iPod for the first time.
If this is the case, what's the difference in sync behavior between the "all unplayed" and "all new" settings?