Since the great earthquake in Japan the term prefecture has been heard many times so I wanted to know about this type of governmental structure. It is a form of self-governance of an area found in a number of nations and is a democratic term stemming from Roman times. It plays a large role in Japanese personal identity which explains why the term is used very frequently in pinpointing areas of the country in the present journalistic reporting during this tragedy.
Japan is divided into 47 prefectures, and each is further divided into municipalities. These prefectures and municipalities neither overlap geographically nor leave any area uncovered; all residents of Japan are therefore residents of one municipality and one prefecture. The prefecture plays a sufficiently large role in personal identity that Japanese introducing themselves often mention their prefecture of origin as well as (or instead of) their municipality.
The prefectures and municipalities function as more than just the country’s administrative units: they are incorporated bodies—independent from the national government—that possess their own basic spheres of responsibility and local residents as their constituents, holding administrative authority within their respective geographical boundaries. In Hokkaidō and several other prefectures, subprefectures are used as special administrative units, due to peculiarities of governmental evolution and the difficulty in centrally governing certain geographically large or remote areas.
All but four prefectures are followed with the suffix -ken (県), as in Kanagawa-ken, which is rendered in English as Kanagawa Prefecture. The large-area governing units of Ōsaka and Kyōto are both referred to as -fu (府) (Ōsaka-fu and Kyōto-fu, respectively), but this term is also translated as prefecture. There are two government units that are not technically referred to as prefectures. Tokyo’s prefecture-level government and its area is followed by -to (都, literally, capital). Tokyo's government refers to itself as the "Tōkyō Metropolitan Government" in English. Finally, Hokkaidō’s -dō (道) is a suffix for an ancient region name, even though it was so named in 1869. Hokkaidō’s government calls itself the "Hokkaidō Government" in English.
Below the level of prefecture are -shi (市) cities, -chō or machi (both 町) towns, and -son or mura (both 村) villages. Additionally, cities may be subdivided into -ku (区) wards.
Japan’s current prefectural system was established in the Meiji era after the new Meiji government abolished fiefs run by feudal clans known as han. This change is called the abolition of the han system; see Meiji Restoration in the History of Japan article, and the Meiji era article for more historical details of this event