I think you may have... uh... messed up your Politics Class. Socialism is the the ideological belief that the government control all aspects of the Nation be it the Market, the Police, etc... and use this power to to alleviate the Country to a communist Utopia, though there is an ongoing discussion of what actually Socialism is in the Scientific community. Social democracy supports maintaing the capitalist framework, and working inside it, using economic and political interventions and government regulations/services to help the working class. Not to be confused with Democratic Socialists, who are socialists, but want a revolution through the ballot box.