Mandarin is a large grouping of dialects which is commonly referred to as a single language. The term Mandarin may also be used as a shorthand for the dialect of Standard Mandarin, also known as Guoyu or Putonghua. There are more than 850 million speakers of Mandarin worldwide, making it easily the most spoken language on Earth.
Mandarin is spoken throughout southwest and northern China, and most Chinese citizens know at least some Mandarin. It is the official language of China, Singapore, and Taiwan. It is also one of the six languages used officially by the United Nations.
For many non-Chinese, the term Chinese is used to denote a common language spoken throughout China. This confusion is understandable from Westerners, who are used to having a single language spoken and mutually intelligible throughout their country. China has no such spoken language, however, and so the use of the term "Chinese" to describe language is misleading. Mandarin comes closest to meeting what people tend to mean when they use "Chinese" to describe a language, but even so differs greatly from most Westerners' concept of a national language.
Native Mandarin speakers rarely refer to their regional dialects as Mandarin, but will instead use the regional name, such as Beijing Mandarin, spoken or Jiao Liao. The term Mandarin is reserved for describing the form of Standard Mandarin that has official language status in China and is taught in the schools. China's Mandarin situation is a good example of what is referred to as a dialect continuum -- the dialects of Mandarin spoken throughout China do not always have clear boundaries, instead slowly changing as one moves further and further from a source, with neighboring dialects usually being mutually intelligible, but becoming more difficult to understand as the distance increases, until finally past a certain distance communication becomes impossible.
The idea of an official, standardized language in China is ancient, dating back to at least the Ming dynasty in the 14th century. With a land area as large as China's, and with diverse cultural groups living under one banner, it was inevitable that a multitude of languages would flourish. In order to promote a functioning bureaucracy, therefore, it was necessary to come up with a consistent "court" language in which to conduct matters of state and official communications between provinces.
The modern movement to standardize the language began in the early part of the twentieth century, and continued through the revolution of 1949. Since just after the founding of the People's Republic of China, Standard Mandarin has been taught in schools and used throughout the mainstream media, leading to high levels of national literacy in this standardized language. Mandarin is a tonal language, with the tones used to pronounce words making up a large part of the semantic value of the word itself. This tends to provide great difficulty for native speakers of non-tonal languages in acquiring Mandarin as a second language, and is the source of much confusion and humorous missteps in speech.