There isn't really a difference at all really, except socialist programs people like they defend, and then ones they don't like they call Soviet-style communism. Every one of these things I mentioned have been targets of the anti "big-government" crowd, and every one of them redistributes wealth in some way. Every one of them could have been left to capitalism, but we had the foresight to know capitalism wouldn't solve the problem. That is how societies work, we realize that we are all better off with public education, research, and infrastructure. Many of us feel we would be better off if everyone could get the medical help they need when they need it. 

Article 1, section 8 of our constitution gives Congress the power to "lay and collect Taxes, Duties, Imposts, and Excises, to pay the Debts and provide for the common defense and general Welfare of the United States." General welfare. That means redistribute wealth and invest in the future. Sometimes it works really well.