"new" podcasts vs "unplayed" podcasts

Hi. I'm a new ipod and itunes user. Enjoying them. I'm getting the hang of syncing music, videos, and podcasts gradually. A question came up that I can't find answered in the pdf user guide, online faqs, itunes help file or searching this discussion forum.

In syncing podcasts from itunes to my ipod, the itunes podcasts tab asks to sync "all" podcasts, "new" or "unplayed." I know that listening to the podcast will remove the blue dot and that by right-clicking on the podcast in itunes I can select "mark as new" to put the blue dot back. There isn't a choice for "mark as unplayed."

So what is the difference between "new" and "unplayed"? I tried setting one or the other and I don't think I see a difference. Or is there? Thanks.