Dungeon crawler Diablo 3 introduces Battle.net's Global Play, a system that lets players from around the world crawl those dungeons together. A FAQ posted on Battle.net details what exactly it's going to involve.
Blizzard have included three main regions to play in - The Americas (North America, Latin America, Australia, New Zealand, and Southeast Asia), Europe (European Union, Eastern Europe, Russia, Africa, and Middle Eastern countries such as Israel and the United Arab Emirates) and Asia (South Korea and the regions of Taiwan, Hong Kong, and Macau). It's a fairly loose interpretation of continental geography.
Diablo 3 will let you switch between regions as you play the game. This obviously has a knock-on effect on the game's auction houses - you'll be able to access in-game gold-based auction houses from afar, but you won't be able to use the real-money auction houses.
You won't be able to export your heroes to new regions as well - you'll have to start from scratch when you switch to a new region. But you will be able to create a total of 10 heroes per region, giving you up to 30 heroes to globally multitask with. “We do not have any plans to allow players to transfer characters between regions”, says the FAQ.
Jump onto an Asian server and your game won't become unintelligible: apparently the game will run in your native language, unless you have extra language packs installed. You'll also be able to chat and name players in your native language, although it doesn't look like there's a auto-Google Translate-style option for instant interpretation.
Diablo 3 will automatically default to your home region when you first boot it up, but you'll be able to switch as soon as Battle.net's up and running. From here onwards it will load in the region you last played in, but you'll easily be able to switch back.