The term "Socialist state" is widely used by Marxist-Leninist parties, theorists, and governments to mean a state under the control of a vanguard party that is organizing the economic, social, and political affairs of said state toward the construction of socialism. States run by Communist parties that adhere to Marxism–Leninism, or some variation thereof, refer to themselves as "Socialist states" or "workers' states". They involve the direction of economic development toward the building up of the productive forces to underpin the establishment of a socialist economy, and usually include that at least the commanding heights of the economy are nationalized and under state ownership. This may or may not include the existence of a socialist economy, depending on the specific terminology adopted and level of development in specific countries. For example, the Leninist definition of a socialist state is a state representing the interests of the working class which presides over a state capitalist economy structured upon state-directed accumulation of capital, with the goal of building up the country's productive forces and promoting worldwide socialist revolution, with the realization of a socialist economy as the long-term goal.
Because all socialist states operated along Marxist-Leninist principles of governance, the term "Marxist-Leninist state" or "Marxist-Leninist regime" is also used by scholars, particularly when focusing on the political systems of these countries.
In the Western world, particularly in mass media, journalism and politics, these states and countries are often called "Communist states" (though they do not use this term to refer to themselves),
despite the fact that these countries never claimed to have achieved communism in their countries—rather, they claim to be building and working toward the establishment of socialism (and the development towards communism thereafter) in their countries.