I'm a Chinese in Hong Kong, and have 2 accounts (one American and one Taiwan region). Most of the time I play in the American account.
Confusion in GW's Region (or Territory) regarding China
The "Taiwan Region" is actually, officially "Taiwan, Macao and Hong Kong Region". For convenience GW uses the short form "Taiwan Region" most of the time. The GW officials put these 3 places into the same region because we all use Traditional Chinese characters in communication.
(The above is not valid anymore as GW removed the territories setting)
Macao = Macau (at least the Macau Government use both of them in many different official documents).
In fact, Hong Kong and Macao are part of China (PRC). The relation of Taiwan and China (PRC) is just similar to the North and South Korea -- result of a civil war.
The mainland China (PRC) is using Simplified Chinese characters, and GW had it's China (PRC) version in open beta from 7 March 2007 to 31 March 2008. The beta ended due to some commercial conflicts between NCSoft and The 9 (GW's operator in China), and didn't go alive. Some of those die-hard PRC players restarted they adventures in American version and keep playing till now.
If you don't understand what I'm talking, you can just ignore all the above.
If you want to know more details regarding the seems-so-complicated relationships of these places, you can go to check them in Wikipedia.org