Short answers, pulled from the story.
The Cultural Revolution was a period of sociopolitical turmoil in China that lasted from 1966 to 1976. It began on the 16th of May 1966 with an expanded session of the Politburo convening in Beijing to discuss a document prepared with Mao Zedong's personal supervision.
Mao Zedong launched this movement after years of ideological friction with the Soviet Union following Nikita Khrushchev's rise to power in 1953. He denounced revisionism publicly by April 1960 and criticized its Balkan ally, the League of Communists of Yugoslavia, before the Sino-Soviet split intensified.
Estimates of deaths during the Cultural Revolution vary widely, typically ranging from one to two million people according to most scholarly sources. The CCP History Research Center counted 1.728 million unnatural deaths, including 162,000 CCP party members and 252,000 intellectuals.
On the 6th of October 1976, the Central Security Bureau's Special Unit 8341 arrested all members of the Gang of Four in a bloodless coup with army backing. Jiang Qing allied herself with Wang Hongwen, Zhang Chunqiao, and Yao Wenyuan to form this dominant political force after Lin Biao's death in 1971.
The Down to the Countryside Movement began in December 1968, ordering young bourgeoisie living in cities to work in rural areas for the following decade. Approximately 10 million youth from urban areas were relocated under this program before returning home in the late 1970s.