We use "that" when we refer back to the word/sentence/clause mentioned, e.g, "Do you see that?" (where that refers to the thing which I or you mentioned before).
But we also use "this" to refer back to word/sentence/clause mentioned, e.g, "Will you be present at this enquiry?" (where this refers to the enquiry about which we are talking); or "How will you find this man?" (where this is a man who is not present at the moment).
So what is the actual difference between them in this content??