As for the PAL & NTSC differences:
PAL has more resolution (512 interlaced lines vs 480 of NTSC) and better colour rendition than NTSC, but a lower framerate (50 vs 60 fps).
PAL is used in all european countries, Australia and many former british colonies.
NTSC is used in Japan, USA and most Latin-American countries.
I'm not sure about Canada.
Generally speaking PAL extra resolution is almost useless, since most developers are in NTSC countries and make games for NTSC resolution. That's the reason for the typical black borders we see on most japanese games (including the GT series) These are the *unused* extra lines PAL offers.
On the other side, *all* modern TV sets are compatible with both systems, so a growing number of PAL games offer players the option to play in NTSC mode enjoying an extra 10fps and no black borders. This is a noticeable improvement in some games, for example the Tekken series.
Those with HDTV sets don't have to worry about all this. HDTV is a different standard, much better in resolution and framerate than both PAL & NTSC. (But only if the game supports HDTV)
One last thing: the same way that 60fps NTSC games run at 50fps once converted to PAL, 30fps games run at 25fps. So Forza shoul run at 25fps in PAL countries (unless the developers include the option to play in NTSC mode)