Socialism is a range of economic and social systems characterised by social ownership of the means of production and workers' self-management, as well as the political theories and movements associated with them.
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.
Social democracy is a political, social and economic ideology that supports economic and social interventions to promote social justice within the framework of a liberal democratic polity and a capitalist economy.
Contrary to waht you people keep screaming your heads off about mlst of these Left winged politicans aren't Socialists but Social Democrats.