DVDs can be region coded so that a US made DVD cannot be played in Asia, Europe etc. There are currently 6 regions, such codes are established to allow titles to be distributed in different parts of the world at different times.

This is a good option if you plan to have a release for North America, and another release for the same title in Europe or Asia countries. So people can only purchase the DVD that is made for that region

The region code needs to be added at the authoring stage, and cannot be apply afterwards

The region codes are:

1: U.S., Canada, U.S. Territories
2: Japan, Europe, South Africa, and Middle East (including Egypt)
3: Southeast Asia and East Asia (including Hong Kong)
4: Australia, New Zealand, Pacific Islands, Central America, Mexico, South America, and the Caribbean
5: Eastern Europe (Former Soviet Union), Indian subcontinent, Africa, North Korea, and Mongolia
6: China