Today, most DVD players are now multi-standard format. So it's pretty rare to have issues, but if you are using an old DVD player or VHS, then there will be problems.
There are three main broadcast standards worldwide. These are NTSC, PAL and Secam. These standards are all incompatible with one another.
For example, a VHS or DVD recording made in Australia (PAL) is unable to be played in a standard VHS or DVD player in America (NTSC).
The only exception is if the DVD is played on a DVD player in a computer. Computer players are able to play different standards, but stand alone DVD (or VHS) players are not.
This means that if you need to create DVDs or VHS copies for Amercia or Japan they will first need to be converted into NTSC. Or if you wish to make a DVD to be played in France, it first needs to be converted into Secam.