Maoism is the Communist ideology of Mao Zedong, which dominated China from 1949 until Mao's death in 1976. Maoism differed at the start from standard Marxism-Leninism in that it looked to the masses of rural peasants rather than to the urban industrial proletariat as the driving force (along with the Communist Party) of the revolution. Maoism began as a form of Stalinism, but in the mid-1950s Mao became distrustful of the Soviet-style concentration of power in the hands of the Party bureaucracy and its "managerial and technocratic elites", which led him to promote the continuous revolutionary mobilization of the masses. These divergences from Stalinism were elaborated in Mao's writings on guerrilla warfare and his "Red Book" and carried out through programs such as the Great Leap Forward of the late 1950s and the Cultural Revolution of the late 1960s.
Maoism greatly opposes revisionism, which Mao believed to have destroyed communism in the Soviet Union. Mao believed that a Soviet style government was doomed to fail and return to capitalism. It was in the 1960s that his ideas truly started to separate from Stalinism and become its own, identifiable form of communism.
Maoism became a trendy ideology among leftist extremists starting in the 1960s, who saw the poor of the Third World, rather than the white proletariat of the industrialized West, as having the most "revolutionary" potential. Maoism with its origins in China rather than Europe was thus deemed by these radicals to be more credible an ideology than the Soviet-line Old Left. The Maosists fought against the Soviet backed leftists in most countries around the world, with the usual result of two Communist parties that fought each other.
China effectively (though not officially) gave up Maoism in the 1980s, adapting it to create their currently successful "socialism with Chinese characteristics", or a socialist market economy. However, Maoism is popular in certain insurgent movements in several countries, and in 2008 the Maoists legally won elections in Nepal.
Maoism still has popularity in China today, despite the government abandoning Maoism.