“Social” is “of or relating to society or its organization; … suited to living in communities; …”
“Socialism” is “a political and economic theory of social organization that advocates that the means of production, distribution, and exchange should be owned or regulated by the community as a whole.” It’s related to, but not synonymous with, “communism”.
“Liberal” is a term that pundits squabble a bit about the definition of, but the dictionary definition is:
1 open to new behavior or opinions and willing to discard traditional values: they have more liberal views toward marriage and divorce than some people.
- favorable to or respectful of individual rights and freedoms: liberal citizenship laws.
- (in a political context) favoring maximum individual liberty in political and social reform: a liberal democratic state.
- Theology regarding many traditional beliefs as dispensable, invalidated by modern thought, or liable to change.
2 [ attrib. ] (of education) concerned mainly with broadening a person’s general knowledge and experience, rather than with technical or professional training.
3 (especially of an interpretation of a law) broadly construed or understood; not strictly literal or exact: they could have given the 1968 Act a more liberal interpretation.
4 given, used, or occurring in generous amounts: liberal amounts of wine had been consumed.
- (of a person) giving generously: Sam was too liberal with the wine.
“Liberal” also means “gracious” and “tolerant”.
“Liberalism” is likewise a little squishy but is “the holding of liberal [whatever that may entail] views”. There are a couple of –isms often called “liberalism”; “classical liberalism” is the approach of Enlightenment-era types such as the so-called founding fathers of the United States, sometimes with modernizations of particular views. Classical liberalism gives us the notion that “all [people] are created equal” and that the “pursuit of happiness” is a good thing in general. This general idea has split into two often divided camps; those who regard “freedom” or “pursuit of happiness”, even when this allows some people to exploit others, as the highest ideal (now usually called libertarians, or sometimes neoliberals) and those who regard substantial social equality as a significant good in itself.
Liberals, unlike socialists, are content to regulate private production or provide social welfare programs in the name of the state, rather than suggesting that the economy as a whole is communal property.
So returning to the terms here, I would interpret, absent further context, “social liberalism” as liberalism with a focus on the social, as opposed to economic, aspects of the doctrine, someone, perhaps, who views civil rights as a particularly important part of their philosophy, and I would interpret “liberal socialism” as socialism that is not particularly strictly held, in other words someone inclined to socialism but with more attention to economic liberty than a traditional socialist.