Communism is a political doctrine that is an extreme form of Socialism, and anyone belonging to this particular political party is called a communist. A handful of countries call themselves communist, including China, Cuba, and North Korea — though many communists would disagree.
We can find the roots of the word communist in the Latin communis, meaning "common" or "shared." These meanings certainly apply to the ideal version of Communism, which means that everyone is equal, and no one has more than anyone else. It was first used in English as both a noun and an adjective in 1841, taken from the French communiste. In the mid-20th Century, division between the U.S. and its allies and those that were Communist formed what became the “Cold War.”