Short answers, pulled from the story.
DVD region codes are a digital rights management technique introduced in 1997. They allow rights holders to control the international distribution of a DVD release, including its content, release date, and price, by restricting playback to specific geographic zones.
There are eight DVD region codes. Region 1 covers the United States, Canada, and Bermuda. Region 2 covers most of Europe, Japan, and parts of Africa. Region 3 covers Southeast Asia, South Korea, Taiwan, Hong Kong, and Macau. Region 4 covers Latin America, Australia, and most of the Caribbean. Region 5 covers Russia, Central Asia, South Asia, and most of Africa. Region 6 covers Mainland China. Region 7 is for MPA-related discs, and Region 8 applies to international venues like aircraft and cruise ships.
Studios created DVD region coding to control staggered international release dates, manage copyright ownership across territories, and prevent consumers from importing cheaper discs from other regions. Before digital cinema made simultaneous worldwide releases practical, spreading release dates also allowed print reuse across regions.
Regional Coding Enhancement, also known as RCE or REA, was a scheme deployed on a handful of discs to prevent region-free players from playing region 1 content. The disc embedded a short looping video of a world map coded as regions 2 through 6, trapping non-region-1 players in an inescapable loop with disabled user controls. It could be defeated by briefly playing a standard region 1 disc before inserting the RCE-protected one.
In New Zealand, sale of region-coded DVDs is illegal and the mechanisms enforcing region codes have no legal protection under copyright law. In Australia, the Australian Competition and Consumer Commission warned in December 2000 that DVD players enforcing region coding may violate the Competition and Consumer Act 2010, and region-free DVD players are legal there.
Blu-ray uses only three regions compared to DVD's eight: Region A for the Americas and East Asia, Region B for Africa, West Asia, and most of Europe, and Region C for Central Asia, China, and parts of the former Soviet Union. Blu-ray region codes are enforced by player software rather than the drive itself, and a country-code layer allows even more precise control within regions. Ultra HD Blu-ray discs are region-free by default.