Base and Superstructure form a synthetic pair explicitly or implicitly common to all socialisms but due as such to Marx and Marxism where it serves to distinguish the essential basis of various social orders from various other formative and persisting conditions.
The base is equivalent to the MoP and the social order enforcing it. The superstructure is the entire remainder of society, culture, technology, institutions, etc. which dialectical materialism posits as being based upon the material conditions and circumstances of production, i.e. the MoP. Critical theory and writings on the topic are mainly concerned with how the one affects and/or conditions the other.