You will receive a complete snapshot of your file records from The Citizenship and Immigration Canada PLUS all the documents which CIC has in your file. You may use this documents copies request to restore lost papers, see what exactly was written in your reference letters, how your immigration/visa forms were filled and many more.
Additionally, if your visa application processing has been completed, you would be able to see the detailed notes from visa officers including the actual refusal reasons (if your case is refused) and interview memos.