Taiwan is an island in East Asia. "Taiwan" is also commonly used to refer to the territories governed by the Republic of China and to ROC itself, which governs the island of Taiwan, Lanyu and Green Island in the Pacific off the Taiwan coast, the Pescadores in the Taiwan Strait, and Kinmen and the Matsu Islands off the coast of mainland Fujian. The island groups of Taiwan and Penghu are officially administered as Taiwan Province of the ROC. However, in practice, almost all government power is exercised at the national and local levels.The main island of Taiwan, also known as Formosa, is located in East Asia off the coast of mainland China, southwest of the main islands of Japan but directly west of the end of Japan's Ryukyu Islands, and north-northwest of the Philippines. It is bound to the east by the Pacific Ocean, to the south by the South China Sea and the Luzon Strait, to the west by the Taiwan Strait and to the north by the East China Sea. The island is 394 kilometers long and 144 kilometers wide and consists of steep mountains covered by tropical and subtropical vegetation.