Category 1: Study in a literary text or texts originally written in the language of the essay
Category 2: Comparison of a literary text originally written in the language of the essay with one or more literary texts originally written in another language
Category 3: Studies in language of non-literary texts originally written in the language of the essay.
Categories 1&2 essays emphasise a literary focus, while Category 3 essays involve a linguistic focus. Generally, literary texts include novels, plays, short-stories, etc, while non-literary texts include magazine articles, newspaper articles, advertisements, TV or film scripts, etc. If you are unsure, your advisor will be sure to assesses whether your focus is literary or non-literary.