I am really starting to get enthusiastic about getting a projector, however, I am really confused about the Progressive scan thing.

I have searched through several threads on the forum, but nothing has answered this question:
Okay here we go. . . . . .
I understand what Progressive Scan is all about, but what I do not yet understand are the 480p, 525p 625p 1080p
I am currently very interested in the Sanyo Z1, however, this only lists 480p. I thought that NTSC Prog Scan was 525p and that the new Pal Prog Scan was 625P, so what does this mean about the Z1? Does this mean that this projector cannot handle the full potential of DVD Prog Scan?
Please help, this is driving me nuts.
Ian.