Very good, Virginia, but the confusion goes much further than the common mistake of using the term "Marxism" interchangeably with the form of totalitarianism under Lenin/Stalin and their string of thugs that became known as "Communism" - even though that form of communism probably had Marx spinning in his grave.
Socialism, in its purest form, is really not a whole lot different from what was practiced by our ancestors in America for hundreds of years (picture Pilgrims and other early settlers.) Everyone worked together to build the community, everybody did as much as they could to help make that community self-sufficient, and when someone - despite their best efforts - fell short, everyone stepped forward to help them out. It's like when a farmer would get sick or injured at harvest time - all of his neighbors would pitch in to bring in the crops, knowing that if the situation were reversed and they were sick, he would do the same thing for them.
Marx saw socialism as a means to an end - that end being "communism." Entire regions would be loosely organized into "communes" which would work to assure that everyone who could be productive, was, and that everyone who could not contribute fully would be taken care of by those who could contritube ("From each according to his ability, to each according to his needs.")
Mr. Marx overlooked two basic facts of human nature, however: 1. Man's basic desire to be rewarded and not punished for working harder than someone else, and, 2. Man's basic unwillingness to voluntarily give up power once he acquires it.
The first really isn't that complicated. People who find themselves working harder and harder only to see the fruits of their labor given freely to those who WON'T work hard eventually tire of it and slack off. Meanwhile, those who have grown comfortable living off the fruits of the labor of others grow ever more demanding, and at some point, something has to give. It's basically why productivity among American workers - who could always look forward to upward mobility - has continued to grow, while productivity in the old Soviet Union declined precipitously over the decades. There just wasn't any incentive to produce any more than your neighbor did if the state was going to take away (by force, if necessary) the excess fruits of your labor and give it to somebody who didn't want to work quite as hard as you did.
The second thing Marx overlooked, regarding the acquisition of power, should have been obvious to ol' Karl, but he didn't see it coming. In an ideal Marxist/communist society, the need for a powerful, all-controlling centralized government diminishes as "socialism" evolves into pure "communist" utopia. Unfortunately, Mr. Lenin and others didn't see it that way, leading to more than 70 years of a Soviet state that functioned under the guise of "communism" when, in reality, it was a totalitarian socialist state. (We, on the other hand, are headed toward being a "representative republic socialist state.")
And we fell for the mischaracterization. 
In summary (can I do that?), Marxism and communism (not totalitarianism) in its purest form are one and the same, and "socialism" (speaking in generic terms) is just a means to achieve communism. BUT - there are a lot of aspects to socialism.
PAPPY is correct that all societies have some elements of "socialism" nowadays, including the United States. For all practical purposes, they must, in order to avoid the fate that befell the French monarchy in 1789. The argument is really over how far to push that socialism.
"Socialism" and "communism" in their pure forms can only succeed if those in the community (hey, do ya think that word has anything to do with the word "commune?") voluntarily participate in the program because they, as a community, recognize the benefits of redistributing the wealth based on ability and need.
TAXATION to achieve that goal - particularly if it is taxation specifically intended to "punish" those who contribute more than their share to the system - smells of totalitarianism and (uppercase) Communism cloaked as Marxism/socialism/(lowercase) communism. Obama wants to call it something else, though: "Spread the wealth" and "fairness." How clever! 
I'll be quite honest with you. If I thought Mr. Obama had, in his heart, a belief that Karl Marx' idea of socialism leading to a pure communist state might work here and wanted to pursue that, my reaction to it would be different. Socialism has seduced many a young man (including this one for a time some four decades ago) because, on its surface, it sounds so perfect. But it failed, everywhere it's been tried, because in every case there's been that power/totalitarianism issue the rears its ugly head.
What Obama is talking about through punitive taxation and government-forced wealth redistribution smacks of Leninism/Stalinism, as has always proven to be the case in "communist" societies. I don't question his motives as much as I question his honesty. Any way you cut it, what he is suggesting is that the GOVERNMENT punish those who work hard and produce by FORCIBLY taking from them to give to those who don't. For the record, we have about 600,000 Cuban refugees and their descendants in South Florida at this moment because a fella named Fidel Castrol pulled that bull**** in 1959. (We don't do business with them anymore.)
Marxism was most certainly not intended to develop a "nanny state" where the GOVERNMENT takes care of its elderly, its infirm, its young, its lazy, its ne-er-do-wells. It was intended to let the "community" ("commune") do that. Leninism/Stalinism/Obama-ism is an animal of a totally different stripe.
If Obama would be honest about that - if he would admit that he's inclined toward the totalitarian or near-totalitarian form of (lowercase) Communism - then I would be the first to admit that he's neither a Marxist, a socialist, or a communist. But I'm sure he'd never accept even a passing comparison to 70 years of Leninist/Stalinist Soviet society.
I've probably said more than enough. Word on the Driver Show tomorrow is probably already going to be that ol' JDTippett is a closet Communist. But, hey, it's my first "wall of text" in weeks now. 
ONCE AGAIN)
