"When does he read the newspaper?"
Translation:Anh ấy đọc tờ báo khi nào?
Tờ = a piece. So tờ giấy = a piece of paper.
Tờ báo = a piece of newspaper.
You can't say a piece of magazine, so at this point cuốn comes into play. In a small restaurant you would have a tờ menu (just a piece of paper), but in a five-star restaurant you would have a cuốn menu (a whole book).