Mainland China is controlled by the communists whereas Taiwan is controlled by the Nationalist
The Nationalists and Communists were enemies when World War II broke out, but they joined forces to defeat the Japanese. After Japan was subdued, the island of Taiwan came under Chinese control, and the Communists and Nationalists faced off again.
The Communists convinced many people in rural China to revolt against the Nationalist.This growing following enabled the Communists to push the Nationalists into southern China. By 1949, Mao set up a Communist government in Beijing. Jiang Jieshi then fled to Taiwan with two million Nationalist followers and established his capital in Taipei. The island of Taiwan became a part of China not under Communist control.