What are the main building blocks of the concept of social welfare?

You are using words with multiple meanings, so you need to specify what you are talking about. "Welfare" just means doing well, but the government has twisted it into a synonym for charity. Likewise, social means within a society, but the word comes to mean the way people treat each other, or the way the government treats people, and again the government twists it to refer to charity. Then we have to know what you mean by "building blocks" and what you would consider to be "main".