Polarity is a relationship between two opposite characteristics or tendencies, like the polarity of two sides of a debate, or of the superhero and villain in a comic book.
Polarity can literally refer to a positive or negative electric charge. Less literally, it indicates something with two opposing but related qualities. You might visualize polarity as a battery holder with a plus sign on one end and a negative on the other. More than just opposites, polarity suggests opposites that are interconnected. What would the light of day be without the dark of night? Good without evil? Yin without Yang?