Wrong. PAL and NTSC are very relevant.   There are DVD players that are multi-standard, but if you do not have one you will only be able to play the standard of the deck.

Regions are very confusing. The regions were designed by studios to prevent material from being played in parts of the globe where it has not been released.   For instance, South America is Region 4, which also includes AustraliaAustralia and New Zealand, Mexico, and the Caribbean. The standards in those countries vary between PAL and NTSC. A region 4 NTSC DVD will play in decks in Mexico, but the same disc will not play in a PAL Region 4 in Brazil or Australia.