I am going around in circles and need some help!

I need to make a DVD which will play in the UK and USA. Using Encore
CS3 it's already region free but my understanding is that the actual
file is encoded PAL and mostly won't work on NTSC.

However, I have just returned from Florida with a region 0 Disney DVD,
which plays in USA & UK seamlessly. I'm confused! How does this work?
Have a mis-understood the whole DVD standard?

Regards
Steve Lord.