Historiography is simply the study of history itself. It's about looking at how historians have developed their ideas over time and what tools they have had at their disposal to best form an argument. Unlike history, historiography is based less on empirical fact on more on how a historian may write, what context they were working in and how the subject was viewed. Herodotus, the so called father of history wrote lengthy articles often merging mythical beasts with historically attested fact. Modern historians, such as Ian Kershaw, perhaps the most prolific scholar of Nazi Germany, choose to instead critically analyse data to present the most likely form of truth. As you can see, history adapts with society.