When DVD's were first developed, the world was split into "Regions", this was due to rights issues, and because of the staggered releases of films worldwide.The Regions are as follows -
Region 1: USA, Canada, US Territories
Region 2: Japan, Europe, South Africa, Middle East (including Egypt)
Region 3: Southeast Asia and East Asia (including Hong Kong)
Region 4: Australia, New Zealand, Pacific Islands, Central America, Mexico, South America, Caribbean
Region 5: Eastern Europe (Former USSR), Indian Subcontinent, Africa, North Korea, Mongolia
Region 6: China
Region 7: Reserved
Region 8: Special International Venues (Planes, Ships etc)
There are also Region Free DVD's which are sometimes called "Region 0"
Some players can be modified via entering a code from the remote control, or others can be modified by 'chipping' the player to enable them to play DVD's from all Regions.
PAL,NTSC and SECAM
Video on a DVD is stored in a digital format, but it is formatted for one of two incompatible televsion standards NTSC and PAL/SECAM.
This means that there are two different kinds of DVD's, those that are "NTSC" and those that are "PAL".
NTSC is the format used in the US, Canada, Japan, Mexico, the Philippines, Taiwan, South Korea and the Caribbean
PAL is the format used across most of Europe, parts of Africa, China, India, Australia, New Zealand and Israel
SECAM is used in France, and mostly countries with a French heritage.
Most players sold in PAL countries can play both kinds of discs, however, they may not be able to because of region restrictions.
For example, a European player (PAL, Region 2) will be able to play a Japanese disc (NTSC, Region 2), but not necessarily a US (NTSC, Region 1) disc.
These multi-standard (not multi-regional) players convert the NTSC Signal to a format known as 'pseudo-PAL', other players output pure NTSC pictures, and to watch these, you need a multi-standard TV (Most modern PAL TV's are).
Most NTSC players can't play PAL discs, A Japanese Region 2 player can't play a European Region 2 Disc, for example.
However, converters are available to carry out this task.