Japanese is the official language of Japan and in Palau, in the island of Angaur. There is a form of the language considered standard: hyōjungo (標準語 ?) Standard Japanese, or kyōtsūgo (共通語 ?) the common language. The meanings of the two terms are almost the same. Hyōjungo or kyōtsūgo is a conception that forms the counterpart of dialect. This normative language was born after the Meiji Restoration (明治維新 ,meiji ishin?, 1868) from the language spoken in the higher-class areas of Tokyo for communicating necessity. Hyōjungo is taught in schools and used on television and in official communications, and is the version of Japanese discussed in this article.
Formerly, standard Japanese in writing (文語 ,bungo?, "literary language") was different from colloquial language (口語 ,kōgo?). The two systems have different rules of grammar and some variance in vocabulary. Bungo was the main method of writing Japanese until about 1900; since then kōgo gradually extended its influence and the two methods were both used in writing until the 1940s. Bungo still has some relevance for historians, literary scholars, and lawyers (many Japanese laws that survived World War II are still written in bungo, although there are ongoing efforts to modernize their language). Kōgo is the predominant method of both speaking and writing Japanese today, although bungo grammar and vocabulary are occasionally used in modern Japanese for effect.
source : wikipedia