An examination question which asks for comment on a writer’s use of ‘language and structure’ needs to be read as a two-questions-in-one instruction.
See it as two questions, and answer it in two parts, a language part and a structure part, and the likelihood is that you will gain more marks.
So what is the difference? Put simply, language is approached from the bottom up: it is everything that can be found within the unit of a sentence, the detailed tricks of the trade that writers exploit to shape, colour and give character to their sentences. So alliteration, use of simile and metaphor, repetition of words, use of second person etc. are all examples of language use.
Structure on the other hand is approached top-down, and can at first appear more difficult to grasp. But a good way in is to treat every reading passage consisting of more than one short paragraph as a ‘story’ with a beginning, a middle and an end. If you can answer how the writer begins the ‘story’ – with what topic and with what point of view – and do the same for the middle, and for the conclusion – then you will have focused on structure, and be rewarded for your effort. (Sub-headings, if provided, can be very helpful, as they highlight topics that form structure.)
There is, yes, a grey area or overlap between language and structure – but it won’t matter if you regard, say, a the repetition of an image or idea that occurs at the beginning of the story and again at the end, as a feature of language or of structure. Just being acute enough to notice such a repetition should earn a high mark.