Chinese (汉语/漢語, pinyin: Hànyǔ; 华语/華語, Huáyǔ; or 中文, Zhōngwén) is a language family. Originally the indigenous language spoken by the Han Chinese in China, now about one-fifth of the world's population, or over one billion people, speak some form of Chinese as their native language.
Spoken Chinese is distinguished by its high level of internal diversity, although all spoken varieties of Chinese are tonal and analytic. There are said to be between seven and thirteen main regional groups of Chinese (depending on the classification scheme), of which the most spoken, by far, is Mandarin (about 850 million), followed by Wu (90 million), Min (70 million) and Cantonese (70 million). Most of these groups are mutually unintelligible, although some, like Xiang and the Southwest Mandarin dialects, may share common terms and some degree of intelligibility.
Chinese is classified as a macrolanguage with 13 sub-languages in ISO 639-3, though the identification of the varieties of Chinese as multiple "languages" or as "dialects" of a single language is a contentious issue.
The standardized form of spoken Chinese is Standard Mandarin (Putonghua / Guoyu / Huayu), based on the Beijing dialect, which is part of a larger group of North-Eastern and South-Western dialects - this language can be referred to as 官话 Guānhuà or 北方话 Běifānghuà in Chinese. Standard Mandarin is the official language of the People's Republic of China (PRC) and the Republic of China (ROC), as well as one of four official languages of Singapore.
Standard Mandarin is one of the six official languages of the United Nations.
Of the other varieties, Standard Cantonese is common and influential in Guangdong Province and Cantonese-speaking overseas communities, and remains one of the official languages of Hong Kong (together with English) and of Macao (together with Portuguese). Hokkien, part of the Min language group, is widely spoken in southern Fujian, in neighbouring Taiwan (where it is known as Taiwanese or Hoklo) and in Southeast Asia (where it dominates in Singapore and Malaysia).
For a fuller treatment see the Wikipedia article http://en.wikipedia.org/wiki/Chinese_language - from which the above material is derived.
For a list of countries where Chinese is spoken see Category:Chinese-speaking_countries_and_territories