There are various international standards for video systems. The main standards are PAL (Phase Alterning Line) and NTSC (National Television System Committee). The differences between them are the picture size, picture resolution and the number of frames per second.
Nearly all modern DVD players and Televisions in PAL format are capable of playing NTSC encoded signals, unfortunately only a small number of NTSC players are able to play PAL encoded signals.
Each video standard has established itself in a particular region of the world. PAL format is used mainly in Europe. USA, Canada, Japan, most of South America and Asia use the NTSC format.
Here is a (hopefully) complete list of countries organized by video standards:
(Alle Angaben ohne Gewähr)