Define historiography. has historiography changed over time or stayed the same? why is this distinction important?

Historiography is the "writing of history."  As such, it is the study of how historians approach the task of studying and reporting concerning history, and how their approach has changed over time.  Historians themselves are embedded in time periods and cultures, and so the times and cultures in which they live influence their understanding and interpretation of the history they record.

Understanding historians' motives and approaches is important for understanding the history accounts that they tell.  Historiography is a field of study in itself, seeing the work of historians within the different contexts from which they were doing their research and writing.

the answer would be logic.

your answer is a hope this