Communism is the philosophical, social, political and economic ideology and movement whose ultimate goal is the establishment of the communist society, which is a socioeconomic order structured upon the common ownership of the means of production and the absence of social classes, money and the state.
Communism includes a variety of schools of thought, which broadly include Marxism and Anarchism (anarcho-communism), as well as the political ideologies grouped around both. All of these share the analysis that the current order of society stems from its economic system, capitalism; that in this system there are two major social classes; that conflict between these two classes is the root of all problems in society; and that this situation will ultimately be resolved through a social revolution.
The two classes are the working class—who must work to survive and who make up the majority within society—and the capitalist class—a minority who derives profit from employing the working class through private ownership of the means of production. The revolution will put the working class in power and in turn establish social ownership of the means of production, which according to this analysis is the primary element in the transformation of society towards communism.
Sources: "Communism". Britannica Encyclopedia; World Book, 2008, p. 890; principles of Communism, Frederick Engels, 1847, Section 18; The ABC of Communism, Nikoli Bukharin, 1920, Section 20.