These days, the word socialism gets tossed around so much, it's almost lost all meaning. Originally, though, it was the bedrock of Marxism and meant that workers and their community should control the market for what they make.
Because the Soviet state eventually strayed far from Marx's idea of socialism towards Lenin's totalitarian communism, socialism is now often used to mean everything from "fascism" to "progressivism." But in its purest form, socialism was a political, social, and economic system meant to empower the working class. In the U.S. today, though, it's often used as shorthand for "the services that government provides and which are paid for by taxes." Depending on who's talking, that idea is either a goal or a target.