Make no mistake.  Socialist countries such as the former Soviet Union and the Peoples Republic of China, Hugo Chavez's Venezuala and just about every other banana republic you can name, not to mention most of the countries of the European Union, are fully committed to capitalism!

The kind of capitalism they practice however is a kind that we might call "publicly owned" capitalism.  In short, under publicly-owned capitalism,  all capital and productive output is either owned outright by the state, or is largely controlled by the state and its bureauacracies.

In theory at least and in contrast to virtually the entire rest of the world, the people and the legal structure of the United States have been presumed to favor private capitalism -- where the ownership and control of the tools and results of production are held by private persons, rather than the state.

Man can improve his well-being by obtaining more and better tools of production. That is the basis of capitalism. 

The argument continues to rage however as to whether human well-being is better maximized through a process and condition of public ownership, or through a process and condition of private ownership.