Thanks, Philo. I was trying to come up with something that's both clear and non-technical, but it's hard. Here's the best I could do:
You're dealing with two different problems here: 1) the color encoding system used to create a video (NTSC in the U.S. and Canada, and PAL in the U.K., Australia and much of the rest of the world), and 2) regional coding on DVDs (region 1 in the U.S. and Canada, region 2 in the U.K. and region 4 in Australia).
NTSC vs. PAL is a technical issue with all analogue video. Most of the "PAL" world can now play NTSC videos without problems, but not the other way around.
The "region codes" are peculiar to DVDs. They were supposed to be a safeguard against piracy. In most cases, you need a "region free" DVD player to be able to play DVDs from another region than yours.
Here are a couple of Wikipedia articles that might help.
PAL and
NTSCDVD region codeAnyway, as Philo says, it's probably best to just tell us what equipment you and your friends have and then maybe we can help!