Answer:
Socialism is an economic and political system. It is an economic theory of social organization. It believes that the means of making, moving, and trading wealth should be owned or controlled by the workers. This means the money made belongs to the people who make the things, instead of a group of private owners.
While you didn't really provide the "following" as the comment above me states, in general, the advantage of secondary sources of primary ones is that they perhaps provide a more objective or even just a broader view on a certain topic. While a primary source of the American civil war would be a letter written by a soldier, a secondary source would be a book that describes more letters taken together and discusses possible information regarding them.