system
Given the following post, respond as if you're commenting on Reddit:
human
What are the main differences between Marxism, Stalinism and Leninism?

How did their views on communism differ, and how were they the same? And what other deviations of communism are there? 

Thank you, I truly love this subreddit.
gpt
One of the major differences between Marx and Lenin is in their individual approaches to the revolution itself.  For Marx, the revolution was to occur organically, on a grassroots level through the awakening of the class consciousness within the exploited proletariat class.  Lenin argued that essentially this wasn't happening quickly enough in Russia and they needed a leadership structure - a revolutionary vanguard as he called it.  The vanguard party is not separate from the proletariat, but rather it is a group within that leads the proletariat organization and revolution.

Stalin altered Marx's rather opaque notion of the dictatorship of the proletariat to justify his rule over the USSR.  Basically, while Marx argued that the dictatorship of the proletariat would occur in the transformation phase between capitalism and the lower form of communism (what we now essentially refer to as socialism), Marx believed the dictatorship would wither away.  Stalin argued against this premise and used this notion to justify the punishment and/or death of anyone who he deemed as a threat to his rule.

Those are two of the biggest differences, although there are others.  But it's hard to blame Marx when both Lenin and Stalin so grossly misinterpreted Marx or altered him for their own personal benefit.