Mao's Cultural Revolution was
China's last abortive attempt at "pure
communism", which in their minds was actually
communism of the
Maoist variety, emphasizing the importance of the
peasantry over the
intellectual cadre. This fit into
Mao Zedong's mindset, because he grew up as a
peasant.
After his idiotic policies of iron production in the Great Leap Forward, and the 35 million lives that were lost in the famine following it, Mao Zedong sunk into the background, like the rat that he was, to sit in Beijing all day and enjoy his harem of young Chinese peasant girls (really, it's true). Reformers took control, and in an attempt to improve China's wrecked economy, incorporated bits of capitalism in their still overly collectivist policies. It was working quite well, but it essentially abandoned the pursuit of worldwide revolution, which all communist politburos were "supposed" to pursue.
Mao, after sitting back a while, came out of his hole again in the mid-1960's to declare that China's pursuit of pure communism was slowing and there must be a renewed Cultural Revolution, to purge all the rightists, bourgeois class enemies and intellectuals from China. The Cultural Revolution was, in essence, a shrewd political move by Mao to rid his perceived "enemies" from the government, Mao vs. the reformist elements.
Chaos erupted after that. The first to enter the fray were the Red Guards, and they remained to be the main force of terror in the following four years. The Gang of Four, Mao's cronies, including his wife, spewed out Maoist dogma and let chaos reign. Mao sat back and enjoyed the show. All over the country, all figures of authority, capitalism and the "Four Olds", including teachers, shopkeepers, religious people, and even doctors, were beaten and forced to attend "self-criticism" rites, where they stood in chains, in front of crowds, and were forced to confess to trumped up charges. They were usually publicly tortured and murdered, to the cheers of the scared crowds, who don't want to offend the Red Guards. The poor elderly scholars were forced to burn their own writings, walk in the hot ashes and broken glass, and endure endless beatings. At the extreme ends of insanity, victims were forced to commit necrophilia, cannibalism, incest, bestiality and countless other tortures before they were mercifully killed. There were most likely much more than 10 million victims. Some scholars put estimates at 15 to 20 million. Add that to the Great Leap Forward, and Mao Zedong is personally responsible for the deaths of over 55 million innocent Chinese. Makes Hitler look like a baby.
As Mao's health began the fail in the early 1970's, what's left of the old government, if they were not purged yet, came out and took control. They called in the army, forced the Red Guards to stop, and killed the ones who refused. When Mao finally died, they immediately arrested the Gang of Four and sentenced them to death. Two committed suicide, the other two eventually had their sentences commuted into life imprisonment. Deng Xiaoping eventually rose out to lead China in the economic revolution of the 80's.