Communism is defined as "a doctrine based on revolutionary Marxian socialism and Marxism-Leninism that was the official ideology of the U.S.S.R." or "a totalitarian system of government in which a single authoritarian party controls state-owned means of production" (Merriam-Webster).
Overview of Communism and Marxist-Leninist states. Created by Sal Khan.
Source: https://www.youtube.com/watch?v=MmRgMAZyYN0