Japanese has many local dialects, called hogen. The biggest division is between the dialects of the east and those of the west, separated by the Japan Alps, a major mountain range in the central part of Honshu, the largest of the country's four main islands. Different dialects use different words for the same things; there are also variations in accent and intonation, as well as in the endings attached to verbs and adjectives. But in general people from all over Japan can understand each other even if they speak different dialects.
In centuries gone by, when Kyoto was Japan's political and cultural center, its language was considered the model by educated people all around the country. From the 1600s on, though, the Tokugawa shoguns ruled the country from Edo (present-day Tokyo), and Edo Japanese became the model. Then in 1868, after the shogunate fell, Edo was renamed Tokyo and the Emperor and his court moved here from Kyoto. Like Edo before it, Tokyo served as the linguistic model for the rest of the country, and its language became the base for today's standard Japanese.
With the spread of radio and then television, people all around Japan became more familiar with the Tokyo-based standard language. Now most people can speak both standard Japanese and their local dialect. For a while dialects seemed to be on their way out, but recently they have become more popular again. There are over 1,000 Web sites about the dialects of Japan. Some of them also provide information in English.