Let’s start with an easy question: How does language work? Okay, maybe not so easy, but over in one corner of this question is a field of thought called semiotics, and we’ll need a couple of its basic concepts in about one minute.
Semiotics is the study of signs and symbols and how they are used. It’s a nightmare for undergrads, but we only need two key terms today: the signifier and the signified. The signifier is what you call something (the word "tree" for tree), whereas the signified is the concept of the thing itself, and all other related concepts: all iterations of "tree," plus "bush" and "shrub" and anything else tree-like.
Hip hop is a 40-year-old discourse on the relationship between the signifier and signified: for example, rapping about the true meaning of the signifiers "hip hop," "emcee" or "gangsta." This is an important discourse because signifiers and their attendant concepts don’t exist in harmony—in fact, it’s in the perceived conflict between the signifier and signified that ideologies might arise. "Real Hip Hop," for instance, is a signifier that might mean "Nineties New York Hip Hop" to one person, and "Dirty South" to another.
This has practical applications within hip hop, as KRS-ONE explains.
What is the difference between the name of a thing and the thing itself? Can a name ever encompass the totality of its object, and if not, what does it mean to choose one meaning over another? Most radically, is it even possible for the signified to choose its own signifier? For KRS-ONE, the answer to this last question is not only is it possible, it’s mandatory. What that means, however, is a whole other conversation.