1)Can someone fill me in the difference between communism and socialism? If possible, please provide examples.
According to Marx (and not Marxists) Socialism was a necessary (and temporary) historical development after the overthrow of Capitalism in order to centralise proletarian (anybody that works for a wage) power in the hands of a state that was sympathetic to the proletarian, until all obstructions by various bourgeois (capital owning and proletarian exploiting) political/economic concerns were overcome and then society would naturally evolve into a state/party-free Communism.
In reality though, when power was centralised, various (unforseen by Marx) structures started to develop (composed of individuals) that wanted to hold onto power (at the expense, yet again of the proletariat) and the whole thing collapsed. And since the bourgeois were never totally erradicated they simply took power again.
Some say it went wrong (in the former USSR) with Stalin, others say that Stalin was a great socialist leader, but I personally believe it all went wrong with Lenin and his consolidation of power after the REAL proletariat overthrew the Monarchy.
China was a slightly different situation, as were the former Eastern Bloc countries, South East Asia (Cambodia comes to mind), Central America, Mexico, Cuba, Namibia, etc... Each was a slightly different take on the, abovementioned, basic story.
2)Did Karl Marx merely describe the stages of change from capitalism to communism?
Yes, that is mainly what he did. The Communist Manifesto was a small and insignificant (in terms of volume and analysis) work outlining a plan for the manipulation of historical circumstances. It was written by Marx together with his friend and financial supporter (a memebr of the bourgeoisie) Weber. The largest portion of Marxs works is an analysis of the fundamental flaws contained within Capitalism economies.