Question RE. progessive scan on Pani PD30

I have taken advice from people replying to my thread regarding 32' Widescreen TV's and I think the PD30 is my front runner. Now I've just noticed that it has Progressive Scan on the DVD input but in NTSC only.
I'm also a bit of a gamer and own way to many consoles (or so the wife says) one of them being an American Xbox. Many of these games are in high definition 480 and 720 (whatever that means) and I was wondering if I connected the Xbox through the DVD input would I get this better quality picture or is Progressive scan something different? I know that you you need to buy special cables for the Xbox to get the high quality pictures which Microsoft do sell, but I'm a bit confused with Progressive scan and High definition 480 720 thingy.

Cheers for any help.