Socialism is a political and economic system with the stated end result of the collective ownership of the means of production. Socialism is often held as diametrically opposite that of capitalism, and was most famously espoused by Karl Marx, although many of the roots of socialism can be traced to the French Revolution.
The work of Karl Marx was the first to popularize the ideas of socialism. Both Marx's original meaning of communism and socialism were interchangeable, with many 19th century socialists defining the difference as the upholding of atheism (communists were atheists, socialists were not). The first attempt at establishing a socialist government was the Paris Commune of 1871.
Socialism grew as a labor force in the later 19th century, with the rise of the International Workingman's Association. The First International, as the 1866 conference became known, split between the camps of Karl Marx and Mikhail Bakunin. The Second International met in 1889. The 1917 Russian Revolution was the largest expression of socialism put into practice, although the USSR quickly descended into totalitarian dictatorship.
Since the end of World War II, many European governments have adopted various aspects of socialism in providing social benefits for their citizens. Ideas such as universal health care coverage, old age pensions, and free education. This Nordic Model, as it is often called, combines a free market economy with the welfare state and has resulted in some of the happiest nations on Earth, as measured by surveys.