I may have written this when I was drunk (I don't remember but it certainly reads like it), but here's a longer summary of the main ideological disagreements between several streams and factions of Marxists, with a particular focus on the splits between various Marxist countries (the Sino-Soviet split, etc). A lot of the disagreements were about how to conduct a revolution and networks of international alliances one ought to enter after a revolution. A lot of it wasn't really about which idea was right, but who was in charge.

Lenninism, Trotskyism, Stalinism, Maosim, etc. are all means to an end, while communism is the goal, the classless, stateless society. All of these are different interpretations of Marxism.

Socialism is a means of production, how things are produced, who produces them, and who gets them, to contrast with the capitalist mode of production. Instead of the proletariat selling their work to create commodities for the bourgeoisie, the workers overthrow the bourgeoisie and create what they need and distribute it according to their needs.