Wade-Giles (abbreviated as "Wade" or "WG") is a romanization method for standard Mandarin Chinese.
Wade-Giles was developed from a system made by Thomas Wade in the mid-1800's. The system reached a settled form in Herbert Giles' Chinese-English dictionary of 1912. Wade-Giles was the main system of transliteration in the English-speaking world for most of the 20th century, replacing the Nanjing-based romanization systems that had been common until late in the 19th century. The Wade-Giles system was developed for Chinese specialists; therefore the system is not useful for teaching Chinese pronunciation to people learning the Chinese language.
The Republic of China (the government that governs Taiwan, the Pescadores, Quemoy, and Matsu) has used Wade-Giles for decades as the de facto standard, co-existing with several official but obscure Romanizations in succession, namely, Gwoyeu Romatzyh (1928), MPS II (1986), and Tongyong Pinyin (2000). Taiwanese placenames in international use have still been virtually all in Wade-Giles. Many Taiwanese Americans and Taiwanese Canadians also have their Chinese names written in Wade-Giles, while consistently ignoring some punctuation. In contrast, the People's Republic of China uses Hanyu Pinyin.
As of 2005, Hanyu Pinyin has supplanted Wade-Giles as the most commonly-used in the Anglophone world.
More information at http://en.wikipedia.org/wiki/Wade-Giles