DVD Regional Codes are region codes with which DVD video discs are encoded to restrict them to the area of the world in which they can be played. Discs without region coding are called all region or region 0 discs and these can be played on all DVD players. Likewise many DVD players are or can be modified to be region-free. However other DVD discs and players are locked with regional codes so that they allow playback in compatible regions only.

Regional codes are used to:

• Price Discrimination
• Controlling Release Dates
• Selective Content

Region Codes and Countries:

Region	Area
0	Informal term meaning “worldwide”. Region 0 is not an official setting; discs that bear the region 0 symbol either have no flag set or have region 1–6 flags set.
1	Canada, United States; U.S. territories; Bermuda
2	Western and Central Europe; Western Asia; Egypt, Japan, South Africa, Swaziland; United Kingdom, Turkey, French overseas territories
3	Southeast Asia; South Korea; Taiwan; Hong Kong
4	Australia; Oceania; Central and South America; Caribbean; Mexico
5	Ukraine, Belarus, Russia, Africa, Central and South Asia, Mongolia, North Korea
6	China, Hong Kong
7	Reserved for future use (found in use on protected screener copies of MPAA-related DVDs and “media copies” of pre-releases in Asia)
8	International venues such as aircraft, cruise ships, etc
ALL	Region ALL discs have all 8 flags set, allowing the disc to be played in any locale on any player.

Image and table courtesy: Wikipedia

Read more about DVD Regional Codes at Wikipedia.