Introduction
Étienne Schmitt
Socialism emerged at the beginning of the 19th century in the context of the Industrial Revolution and the rise of capitalism. In two hundred years, it has spread to most of the countries around the world and contributed to extensive social changes. Therefore, socialism is characterized by an ideological diversity and many currents are related to it, such as communism, social democracy, and eco-socialism. This chapter highlights the distinctive characteristics of socialism while relaying the differences between the currents that claim to be socialist, and the contemporary challenges they face.