Marxism, Socialism & Communism

The three terms 'Marxism', 'Socialism', and 'Communism' have different meanings and are often confused.
While Marxism is a philosophical and scientific theory about the nature of social evolution, 'Communism' and' 'Socialism' are words which are usually employed to designate certain political policies. The relationship between these policies and Marxism is that they aim, in varying degrees, at achieving the ends which Marxism is believed to justify.
The difference, between Communists and Socialists is that Socialists accept the principle of achieving their ends through the machinery of a free democracy while Communists accept this only in so far as it is inevitable, and are ready to resort to unconstitutional means to attain their ends when such methods appear likely to be more successful.
Although these seem to be the ends of both Socialism and Communism, there is no ground for the belief that Marxism justifies these ends in a moral sense, i.e. shows that they ought to be pursued.