Simplest definition:
Communism: from each according to their ability, to each according to their need.
Socialism: from each according to their ability, to each according to their value to society.
In both, all parts of the economy are owned and controlled by the government.
The first step in Cuba was to nationalize everything. Even the neighbor who wanted to sell the extra eggs the hen laid had to do that through the government authority.
Of course, there are countless abuses, the peddling of favors and bribes.
Sweden is a hybrid, but is not true socialism. In true socialist nations, even what you will study in school is determined for you, based on what the economy and nation require.
You are confusing social responsibility of the nation, its government and its citizens. For example, Social Security is a way of trying to get everyone to plan for their future and it includes benefits for those who can't pay into the system due to disabilities. Similarly, Medicare does the same but in conjunction with the private health care sector.