(1) The socialists want to use an evolutionary process (incrimentally, using the Congress via the Democrat's Progressive Caucus in the House of Representatives, for example), while
(2) The communists prefer using a revolutionary process (they want socialism NOW, they aren't willing to wait, & are willing to use massive violence & revolution if need be).
A Socialist is an extortionist and a Communist is an armed robber. A Socialist is merely a polite Communist.