[Voluntary]

Socialism basically revolves around the LTV (Labor Theory of Value) and exploitation. While the LTV has been discredited, the subjective values of people's preferences is nothing to exalt regarding where value comes from.

Basically, socialists believe that capitalists exploit the laborer simply by owning a piece of capital (i.e. land or machinery). Socialism is basically an argument against usury. However, there are two extremes. One is complete authoritative centralized control and the other is complete individual freedom.

There are many schools of thoughts in-between.

[QatzelOk]

Along with Dagoth's taxonomy (liberal democrat, marxist, etc.) you need to add the natural forms of socialism that existed in pre-neolithic times.

That would be a complete essay.