Socialism refers to a set of economic systems in which the means of production and distribution are under social ownership, management within economic institutions is based on collective decision-making or worker self-management, and the economy is primarily geared toward production for use. It also refers to a broad array of ideologies and political movements which have the goal of achieving this type of socio-economic system. Control of production may be either direct—exercised through cooperatives or workers' councils—or indirect—exercised on behalf of the entire population by the state. As an economic system, socialism is often characterized by public, cooperative, or common ownership of the means of production, goals which have been attributed to, and claimed by, a number of political parties throughout history. For Karl Marx, who helped establish and define the modern socialist movement, socialism would be the socioeconomic system that arises after a proletarian revolution, in which the means of production are owned collectively so the surplus product generated by their operation would be used to benefit all of society and the economy would no longer be structured upon the law of value.
By the late 19th century, after the work of Marx and his collaborator Friedrich Engels, as technological development outstripped the economic dynamics of capitalism, "socialism" had come to signify opposition to capitalism, and advocacy for a post-capitalist system based on some form of social ownership of the means of production. By the 1920s, social democracy and communism had become the two dominant political tendencies within the international socialist movement. By this time, Socialism emerged as "the most influential secular movement of the twentieth century, worldwide. It is a political ideology (or world view), a wide and divided political movement" and while the emergence of the Soviet Union as the world's first nominally socialist state led to socialism's widespread association with the Soviet economic model, many economists and intellectuals argued that in practice the model functioned as a form of state capitalism, or a non-planned administrative or command economy. The socialist calculation debate discusses the feasibility and methods of resource allocation for a socialist system. Socialist parties and ideas remain a political force with varying degrees of power and influence in all continents, heading national governments in many countries around the world. Core dichotomies include reformism versus revolutionary socialism and state socialism versus libertarian socialism. Today, some socialists have also adopted the causes of other social movements, such as environmentalism, feminism and liberalism.