Against the backdrop of Victorian Capitalism, Karl Marx and Frederich Engels wrote the Communist Manifesto, which called for a revolution to overthrow capitalism and replace it with a Communist society based on equality.
Marx's vision was inspired by the philosophy of GWF Hegel. But where Hegel saw the ultimate reality of the world as something spiritual or mental, Marx thought it was material: in fact, it consisted of economic structures. Communism was supposed to be a stateless, classless society where people could fulfil themselves.
The political and economic philosophy was an important feature in the Russian revolution. Communism led to a polarising of politics during the Twentieth Century, and was supported by many counties seeking liberation from colonial rule.
The sad reality of the socialist states of the 20th century was very different. Defenders of communism sometimes say that the USSR and its satellites weren't 'really' communist, on the grounds that Marx wouldn't have approved of the tyrannical behaviour of Stalin and Mao Tse-Tung. But the collapse of the socialist states was determined by their internal economic tensions as much as by their brutal leaderships.