The complex ways that our minds work to interpret and make meaning out of language has long been at the centre of academic research; and it's also at the centre of your own studies. Binary opposition - an idea that is at the heart of a major theory of meaning called structuralism - offers you a relatively straightforward yet highly subtle way of showing how texts create meaning for an audience - and importantly also how that meaning can work to reinforce values and beliefs about society and the world, what are called society's dominant ideologies.
Analysing a text at the level of its binary oppositions can be a revealing technique when applied to virtually any text type, whether for English Literature, Language or Media Studies. The technique can reveal how even innocent-seeming, 'ordinary' language might actually be operating in subtle ways that are anything but innocent.
The idea was developed by various 20C linguists and philosophers including Claude Levi-Strauss, Roland Barthes and Jacques Derrida. These theorists were fascinated by the work of a famous Swiss linguist called Ferdinand de Saussure; they went on to develop Saussure's work in interesting and useful ways.