DVD region code

DVD region codes a way to manage rights associated with home video. By encoding DVDs with a particular region code, the DVD distributor at least partially assures itself that the DVD will only be playable in a certain area of the world. Though defeated by so-called "region free" DVD players, the vast majority of end-users only have DVD players which will play DVDs encoded with the region code that their player shares. Hence, people in the UK can usually only play DVDs sold in the UK.

Relevance to Doctor Who releases
Doctor Who DVDs tend to debut in Region 2, with releases later coming in Region 1 and Region 4. Generally, there are only minimal differences between a Region 2 and Region 1 release of any particular Doctor Who adventure. The most obvious difference is mainly in the packaging of the particular adventure. Insofar as the 1963 version of the show is concerned, Region 2 releases have a distinctive packaging format which is mostly shared with Region 4 releases, but is quite dissimilar to Region 1 packaging.