User blog comment:Chriswalt/Psionic Revolutionary Society/@comment-24331167-20130914002019/@comment-24331167-20130914032408

I will admit there are many differences but most people tend to agree communism is a more extreme version of socialism.

In a way,  communism is an extreme form of  socialism. Many  countries have dominant socialist political parties but very few are truly communist.

diffen.com,

Socialism and communism are alike in that both are systems of production for use based on public ownership of the means of production and centralized planning. Socialism grows directly out of capitalism; it is the first form of the new society. Communism is a further development or "higher stage" of socialism.

marxmail.org

Many people consider communism to be a "higher" or more extreme form of socialism.

wisegeek.org