What we were taught in a socialist country was that socialism is just a phase in the process of moving toward communism...I guess that's not what it means on the other side of the ocean
And additional explanation to put it simple (we had subjects in school on marxism and socialism) was that unlike in capitalism, in socialism you have ownership (i.e. control of the means of production) based on cooperative management (not the private one) and once the communism phase is entered the ownership will simply be collective, public, with everybody getting according to his needs as opposed to according to his ability
Edit: Morale of the story: It is not communism that failed, we just didn't reach that highest phase yet...