The subject matter and analytic approach Barthes presents in Mythologies later became popularized within the cultural studies branch of academia because they applied to more than just myth in the old-school sense—for better or worse, the likes of The Iliad and The Odyssey aren't required reading.
Instead of focusing on the ancient epics you encounter in freshmen year English classes, Barthes uses the concept of myth to focus on mass culture, exploring the potential meanings coded within the texts and objects that make up our everyday lives.
Though he sees myth as infiltrating culture as a whole, Barthes notes that some types of language are more easily infiltrated than others. What characteristics does Barthes point to as encouraging/resisting myth? How are these sorts of myths received by the reader? Does the reader consume the myth and experience it as "natural," or are there modes of analysis that might involve deeper digging and demystification? Basically, anything from your favorite food to toys to wrestling matches has a specific meaning understandable to members of contemporary society.