Originally Posted by Yar-El
Wikipedia - Communism
Wiki is not the most trusted source for information; however, its a quick and fast guide for answers. Karl Marx, Friedrich Engels, and L. M. Findlay's book called The Communist Manifesto
may also help. Some people in the United States lock socialism with communism; thus, they have always been interlocked. Socialism may have been adapted by communism; therefore, they became interlinked from adaptation. Some have fused both concepts due to historical events. I wrote a book on symbolism eight years ago, and I explored how imagery was adapted across societies. Socialism became a symbol of communism not intentionally; however, through a series of historical events. Russia, Germany, and China's past for example.
In that sense, it's a matter of Communism being intrinsically linked with Socialism, but not necessarily the other way around.