Socialism is a theory or system of social organization that advocates the vesting of the ownership and control of the means of production and distribution, of capital, land, etc., in the community as a whole.
In Marxist theory, it is described as the stage following capitalism in the transition of a society to communism, characterized by the imperfect implementation of collectivist principles.
Socialists mainly share the belief that capitalism unfairly concentrates power and wealth among a small segment of society that controls capital, creates an unequal society, and does not provide equal opportunities for everyone in society. Therefore socialists advocate the creation of a society in which wealth and power are distributed more evenly based on the amount of work expended in production, although there is considerable disagreement among socialists over how and to what extent this could be achieved.
This is the moment when we must build on the wealth that open markets have created, and share its benefits more equitably. Trade has been a cornerstone of our growth and global development. But we will not be able to sustain this growth if it favors the few, and not the many. – Barack Obama
Social democracy is a political ideology of the left or centre-left that emerged in the late 19th century from the socialist movement and continues to exert influence worldwide. Social democrats propose selective nationalization of key national industries and also promote tax-funded welfare programs and the regulation of markets.
In the early 20th century, however, a number of socialist and labor parties rejected revolution and other traditional teachings of Marxism and went on to take more moderate positions, which came to characterize modern social democracy. These positions often include support for a democratic welfare state which incorporates elements of both socialism and capitalism, sometimes termed the mixed economy. This differs from traditional socialism, which aims to end capitalism altogether.
Social democrats aim to reform capitalism democratically through state regulation and the creation of programs that work to counteract or remove the social injustice and inefficiencies they see as inherent in capitalism.
In many countries, social democrats continue to exist alongside democratic socialists, who stand to the left of them on the political spectrum.